HP 5920 User manual

HP 5920 & 5900 Switch Series
TRILL
Configuration Guide
Part number: 5998-6656
Software version: Release 2416
Document version: 6W100-20150130

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herein.

i
Contents
Configuring TRILL·························································································································································· 1
Overview············································································································································································1
Basic concepts ··························································································································································1
TRILL frame formats···················································································································································1
How TRILL works·······················································································································································3
TRILL forwarding mechanisms ·································································································································3
Protocols and standards ··········································································································································6
Configuration restrictions and guidelines·······················································································································7
TRILL configuration task list···············································································································································7
Enabling TRILL····································································································································································8
Configuration restrictions and guidelines ··············································································································8
Configuration procedure ·········································································································································9
Configuring the system ID and nickname for an RB······································································································9
Configuring the link type of a TRILL port······················································································································ 10
Configuration restrictions and guidelines ··········································································································· 10
Configuration procedure ······································································································································ 10
Configuring the DRB priority of a TRILL port················································································································ 11
Configuring the link cost for a TRILL port····················································································································· 11
Configuring announcing VLANs and the designated VLAN ····················································································· 12
Configuring TRILL timers ················································································································································ 12
Configuring TRILL LSP parameters and features·········································································································· 13
Setting TRILL LSP parameters ································································································································ 13
Enabling TRILL LSP fast advertisement ················································································································· 15
Enabling TRILL pseudonode bypass····················································································································· 16
Setting the SPF algorithm parameters ·························································································································· 16
Configuring TRILL distribution trees ······························································································································ 16
Setting basic distribution tree parameters ·········································································································· 16
Enabling TRILL distribution tree multithread calculation····················································································· 17
Enabling load balancing over TRILL distribution trees ······················································································· 17
Configuring TRILL ECMP routes····································································································································· 18
Enabling incremental flush for TRILL multicast routing entries···················································································· 19
Configuring a TRILL VR ·················································································································································· 19
Creating a TRILL VR ··············································································································································· 19
Associating a TRILL VR with a track entry ··········································································································· 20
Permitting a non-TRILL device to learn the MAC address of the TRILL VR································································· 21
Enabling MAC address retaining on TRILL ports ········································································································ 21
Enabling logging of TRILL neighbor changes·············································································································· 21
Configuring SNMP for TRILL·········································································································································· 22
Enabling TRILL to forward traffic from EVB S-channels······························································································· 22
Configuring TRILL GR ····················································································································································· 23
Associating a TRILL port with a track entry·················································································································· 23
Displaying and maintaining TRILL································································································································· 24
TRILL configuration example·········································································································································· 25
Network requirements··········································································································································· 25
Configuration procedure ······································································································································ 26
Verifying the configuration··································································································································· 29
Support and other resources ·····································································································································31
Contacting HP ································································································································································ 31

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Subscription service ·············································································································································· 31
Related information························································································································································ 31
Documents······························································································································································ 31
Websites································································································································································· 31
Conventions ···································································································································································· 32
Index ···········································································································································································34

1
Configuring TRILL
TRansparent Interconnection of Lots of Links (TRILL) uses IS-IS to provide transparent Layer 2 forwarding.
Overview
TRILL combines the simplicity and flexibility of Layer 2 switching with the stability, scalability, and rapid
convergence capability of Layer 3 routing. All these advantages make TRILL very suitable for large flat
Layer 2 networks in data centers.
Basic concepts
•RBridge—Routing bridge (RB) that runs TRILL. RBs are classified into ingress RBs, transit RBs, and
egress RBs, depending on their positions in the TRILL network. A frame enters the TRILL network
through an ingress RB, travels along transit RBs, and leaves the TRILL network through an egress RB,
as shown in Figure 2.
•TRILL network—A Layer 2 network comprised of RBs, as shown in Figure 3.
•System ID—Unique identifier of an RB in the TRILL network. The system ID is 6-byte.
•Nickname—Address of an RB in the TRILL network. The nickname is 2-byte.
•Link State Database—The LSDB contains all link state information in the TRILL network.
•Link State Protocol Data Unit—An LSP describes local link state information and is advertised
between neighbor devices.
•Designated Routing Bridge (DRB)—Similar to the designated IS (DIS) in IS-IS, a DRB exists in a
broadcast network. It helps simplify network topology, and assigns AVFs and appointed ports for
the VLANs on each RB in the broadcast network.
•Appointed VLAN-x Forwarder (AVF) and appointed port—To avoid loops, TRILL requires all traffic
of a VLAN on a broadcast network to enter and leave the TRILL network through the same port of
an RB. The RB is the VLAN's AVF, and the port is the VLAN's appointed port.
For more information about LSDB, LSPDU, and DIS, see Layer 3—IP Routing Configuration Guide.
TRILL frame formats
TRILL frames include protocol frames and data frames.
TRILL protocol frames include TRILL Hello, LSP, CSNP, PSNP, MTU-probe, and MTU-ack. These protocol
frames use 802.1Q encapsulation and have a fixed destination multicast address 0180-C200-0041.
TRILL data frames have a specific format, as shown in Figure 1. A TRILL header and an outer Ethernet
header are added to the original Ethernet frame.

2
Figure 1 TRILL data frame format
Table 1 describes the fields in the TRILL header.
Table 1 TRILL header fields
Field Descri
p
tion
Ethertype The Ethertype is fixed to TRILL.
V Version number, which is 0. When an RB receives a TRILL frame, it checks the V
field and drops the frame if the Vfield is not 0.
R Reserved for future extension. An ingress RB sets the R field to 0when adding a
TRILL header. Transit RBs and egress RBs ignore the field.
M
Multidestination attribute:
•0—Known unicast frame.
•1—Multidestination frame (multicast, broadcast, or unknown unicast frame).
Op-Length Length of the Options field. 0indicates that the Options field does not exist.
Hop Count Hop count, which is used to avoid loops. An RB drops a TRILL frame whose hop
count is decremented to 0.
Egress RB Nickname Nickname of the egress RB.
Ingress RB Nickname Nickname of the ingress RB.
Options Options field. This field exists when the Op-Length field is non-zero.

3
How TRILL works
TRILL establishes and maintains adjacencies between RBs by periodically advertising Hello frames,
distributes LSPs among RB neighbors, and generates an LSDB for all RBs in the network. Based on the
LSDB, each RB uses the SPF algorithm to calculate forwarding entries destined to other RBs.
TRILL forwarding mechanisms
TRILL uses different mechanisms to forward Layer 2 and Layer 3 traffic. The following sections describe
these mechanisms.
Layer 2 forwarding mechanisms
TRILL forwards the traffic within a VLAN by using the following mechanisms:
•Unicast frame forwarding mechanism.
As shown in Figure 2, a unicast frame is forwarded as follows:
a. When a unicast frame enters the TRILL network, the ingress RB encapsulates the original
Ethernet frame with the following headers:
−A TRILL header (similar to an IP header).
−An outer Ethernet header (similar to the Ethernet header of a regular Ethernet frame).
b. RBs forward the frame hop by hop according to the egress RB nickname in the TRILL header in
the same way routers forward IP packets. Each hop replaces the outer Ethernet header with an
appropriate outer Ethernet header, and decrements the hop count in the TRILL header.
c. Upon receiving the TRILL frame, the egress RB de-encapsulates it to obtain the original Ethernet
frame, and sends the frame to the target device.
Figure 2 Layer 2 unicast frame forwarding flow
VLAN 10 VLAN 200 VLAN 300 VLAN 10
Ingress RB
RB 1
S1 S2
Ethernet frame TRILL frame TRILL frame Ethernet frame
Egress RB
RB 3
Transit RB
RB 2
Ingress RB = RB 1
Outer VLAN = 200
Egress RB = RB 3
Outer S-MAC = RB 1
Outer D-MAC = RB 2
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = S2
Ingress RB = RB 1
Outer VLAN = 300
Egress RB = RB 3
Outer S-MAC = RB 2
Outer D-MAC = RB 3
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = S2
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = S2
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = S2
Unicast frame

4
The outer Ethernet header enables traditional Ethernet switches to forward TRILL frames and
connect RBs.
•Multidestination frame forwarding mechanism.
In a TRILL network, RBs perform the following tasks:
{Compute a TRILL distribution tree for each VLAN based on the LSDB.
{Guide the forwarding of multidestination frames in each VLAN by using its TRILL distribution
tree.
As shown in Figure 3, when a multicast frame from VLAN 10 enters the TRILL network, RB 1, which
is an ingress RB, encapsulates the multicast frame into a TRILL frame. In the frame, the egress RB is
RB 2, the root bridge of the TRILL distribution tree for VLAN 10. When the frame arrives at the root
bridge, it is distributed throughout the TRILL distribution tree. Then, the TRILL frame is
de-encapsulated by RB 3 and sent to the destination station S2. Because the network segment
where RB 4 resides does not have a receiver of this frame, RB 4 drops the frame.
Figure 3 Layer 2 multicast frame forwarding flow
TRILL selects distribution trees for forwarding multidestination frames based on the VLANs to which
the frames belong. Because the topologies of TRILL distribution trees are different, traffic can be
load shared. However, equal-cost links are not used for load sharing.
When N equal-cost links exist in the network, each TRILL distribution tree selects the link with the
largest pseudonode ID for forwarding packets. As shown in Figure 4, two equal-cost links exist
between RB 1 and RB 3. Assume the link directly connecting RB 1 to RB 3 has the largest
pseudonode ID. Both the TRILL distribution tree rooted at RB 3 and the TRILL distribution tree rooted
VLAN 10VLAN 10
S1 S2
VLAN 200
TRILL network
RB 1
Ethernet frame
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = Multi
TRILL frame
Ingress RB = RB 1
Outer VLAN = 200
Egress RB = RB 2
Outer S-MAC = RB 1
Outer D-MAC = All RBs
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = Multi
TRILL frame
Ingress RB = RB 1
Outer VLAN = 200
Egress RB = RB 2
Outer S-MAC = RB 2
Outer D-MAC = All RBs
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = Multi
RB 4
RB 3
Ethernet frame
Payload
Inner VLAN = 10
Inner S-MAC = S1
Inner D-MAC = Multi
RB 2
Multicast frame Distribution tree
of VLAN 10
Root bridge of
distribution tree
Leaf of
distribution tree

5
at RB 4 select the link. For more information about pseudonode IDs, see Layer 3—IP Routing
Configuration Guide.
Figure 4 Multicast ECMP
TRILL distribution trees support Equal Cost Multiple Path (ECMP), also known as multicast ECMP.
When multicast ECMP is enabled, TRILL assigns equal-cost links to multiple TRILL distributions trees.
This improves the load sharing performance.
When N equal-cost links exist in the network, each TRILL distribution tree selects an equal-cost link
for forwarding packets through J mod N in root bridge priority order. J is the priority sequence
number of a TRILL distribution tree and starts from 0.
As shown in Figure 4:
{The link directly connecting RB 1 to RB 3 is assigned to the TRILL distribution tree rooted at RB
3.
{The link RB 1-RB 2-RB 3 is assigned to the TRILL distribution tree rooted at RB 4.
TRILL distribution trees support fast root switching. When an RB detects that the root of a
distribution tree is unreachable, the RB deletes the LSP of the root from its LSDB. This triggers
recalculation of all distribution trees in the TRILL network. Multidestination traffic is switched to new
distribution trees.
Layer 3 forwarding mechanisms
As shown in Figure 5, distribution layer devices RB 1 and RB 2 are gateways of a data center network.
Because of hardware limitations, RBs cannot perform Layer 3 forwarding before TRILL encapsulation or
after removing TRILL encapsulation.
To support Layer 3 forwarding, TRILL virtualizes the gateway RBs into a virtual router (VR). The VR
provides gateway services at a virtual IP address.
Cost=3
Cost = 2
Cost = 1
RB 1
RB 2 RB 3 RB 4

6
Figure 5 TRILL Layer 3 forwarding
A TRILL VR contains multiple member RBs that are configured with the same virtual IP address. All
member RBs participate in Layer 3 forwarding. A master RB responds to ARP or ND requests. The master
RB is elected by using the following rules:
•The member RB with the highest priority is elected as the master RB. The master election priority is
64 by default, and it is not configurable.
•If member RBs have the same priority, the member RB with the highest system ID is elected.
TRILL uses the following mechanisms to forward Layer 3 traffic:
•Unicast traffic forwarding mechanism—Access RBs forward original unicast frames to the TRILL VR.
Member RBs of the VR then perform Layer 3 forwarding for the frames.
•Multidestination traffic forwarding mechanism—To forward multidestination traffic, you must
enable IGMP/MLD snooping and dropping unknown multicast data on all RBs. In this way, router
ports and member ports in Layer 2 multicast forwarding entries are appointed along TRILL
distribution trees. Access RBs forward original multidestination frames to the TRILL VR through TRILL
distribution trees. Member RBs of the VR then perform Layer 3 forwarding for the frames.
Each VLAN supports only one TRILL distribution tree. If you configure multiple distribution trees for
a VLAN, the distribution tree with the lowest root nickname takes effect.
Protocols and standards
•RFC 6325: Routing Bridges (RBridges): Base Protocol Specification
•RFC 6326: Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS
•RFC 6327: Routing Bridges (RBridges): Adjacency
•RFC 1195: Use of OSI IS-IS for Routing in TCP/IP and Dual Environments

7
Configuration restrictions and guidelines
When you configure TRILL, follow these restrictions and guidelines:
•Configuration in Layer 2 Ethernet interface view takes effect only on the current port. Configuration
in Layer 2 aggregate interface view takes effect on the current interface and its member ports.
Configuration on the member port of an aggregate interface takes effect after the member port
leaves the aggregation group.
•To connect a spanning tree network to a TRILL network, make sure the following requirements are
met:
{The spanning tree protocol is disabled on the TRILL network.
{An edge port is used to connect the spanning tree network to the TRILL network. The edge port
can transit to the forwarding state before DRB election is finished. This prevents multiple DRBs
from being elected.
For more information about spanning tree protocols, see Layer 2—LAN Switching Configuration
Guide.
•HP recommends not enabling loop detection on TRILL ports, because TRILL avoids loops. For more
information about loopback detection, see Layer 2—LAN Switching Configuration Guide.
•If IRF is used, retain the IRF bridge MAC address permanently. Otherwise, traffic interruption might
occur after an IRF split. For more information about IRF configuration, see IRF Configuration Guide.
•Do not configure the TPID for VLAN tags on RBs. For more information about TPIDs, see Layer
2—LAN Switching Configuration Guide.
•To avoid loops, do not connect multiple TRILL ports of an RB to a broadcast network, because TRILL
ports cannot detect each other when they are on a broadcast network. If there are multiple TRILL
ports, they might be elected as the appointed ports of a VLAN at the same time and result in loops.
•For the TRILL network to forward Layer 3 multidestination traffic correctly, make sure the following
requirements are met:
{The IGMP/MLD snooping version must be the same on all RBs.
{IGMP or MLD must be enabled on the access-facing VLAN interfaces on gateway RBs to prevent
topology changes from interrupting traffic.
•Enabling PIM-DM or IPv6 PIM-DM on core layer and distribution layer devices might cause multicast
traffic duplication. HP recommends that you use other Layer 3 multicast protocols.
TRILL configuration task list
Tasks at a
g
lance
(Required.) Enabling TRILL
(Required.) Configuring the system ID and nickname for an RB
(Optional.) Configuring the link type of a TRILL port
(Optional.) Configuring the DRB priority of a TRILL port
(Optional.) Configuring the link cost for a TRILL port
(Optional.) Configuring announcing VLANs and the designated VLAN
(Optional.) Configuring TRILL timers

8
Tasks at a
g
lance
(Optional.) Configuring TRILL LSP parameters and features
(Optional.) Setting the SPF algorithm parameters
(Optional.) Configuring TRILL distribution trees
(Optional.) Configuring TRILL ECMP routes
(Optional.) Enabling incremental flush for TRILL multicast routing entries
(Optional.) Configuring a TRILL VR
(Optional.) Permitting a non-TRILL device to learn the MAC address of the TRILL VR
(Optional.) Enabling MAC address retaining on TRILL ports
(Optional.) Enabling logging of TRILL neighbor changes
(Optional.) Configuring SNMP for TRILL
(Optional.) Enabling TRILL to forward traffic from EVB S-channels
(Optional.) Configuring TRILL GR
(Optional.) Associating a TRILL port with a track entry
Enabling TRILL
After you enable TRILL on a port, TRILL can operate correctly by using default settings. A port with TRILL
enabled is called a TRILL port.
Configuration restrictions and guidelines
When you enable TRILL, follow these guidelines:
•To enable TRILL on a port, first enable TRILL globally.
•Enable or disable TRILL on all ports in a VLAN, so that the ports in a VLAN have the same TRILL
status (enabled or disabled).
•Do not enable both TRILL and EVB on a port. If the trill evb-support command is not executed on an
EVB-enabled port, make sure the allowed VLANs of the port do not overlap with those of a
TRILL-enabled port. For more information about EVB, see EVB Configuration Guide.
•When you set up a TRILL network, avoid the case that multiple TRILL neighbors are established for
one RB port. When you plan a network, avoid the networks shown in Figure 6 and Figure 7.
{Figure 6 shows a typical network where two TRILL neighbors are established for the same port
of an RB.
{In Figure 7, because TRILL is not enabled on the port connecting RB 2 to RB 3, the port will
transparently transmit the TRILL Hello frames from RB 3. As a result, two TRILL neighbors are
established for the port connecting RB 1 to RB 2.

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Figure 6 Two TRILL neighbors are established for a port (1)
Figure 7 Two TRILL neighbors are established for a port (2)
Configuration procedure
To enable TRILL:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable TRILL globally
and enter TRILL view. trill By default, TRILL is disabled globally.
3. Return to system view. quit N/A
4. Enter Layer 2 Ethernet
or aggregate interface
view.
interface interface-type
interface-number N/A
5. Enable TRILL on the
port. trill enable By default, TRILL is disabled on a port.
Configuring the system ID and nickname for an RB
The system ID and nickname of an RB are identifiers of the RB in the TRILL network.
•System ID—Unique identifier of an RB in the TRILL network. The system ID can be automatically
assigned or manually configured.
•Nickname—Address of an RB in the TRILL network. The address can be automatically assigned or
manually configured. When multiple RBs in the TRILL network have the same nickname, the RB with
the highest priority uses the nickname. When the RBs also have the same priority, the RB with the
Traditional Ethernet
switch
RB 1
RB 2 RB 3
TRILL enabled port

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highest system ID uses the nickname. The system automatically assigns new nicknames to the other
RBs.
The system resets the TRILL process when the RB's system ID changes.
To configure the system ID and nickname for the RB:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter TRILL view. trill N/A
3. Configure the system
ID for the RB. system-id system-id
By default, the RB automatically generates a
system ID based on its MAC address upon
startup.
4. Configure the
nickname for the RB.
nickname nickname [ priority
priority ]
By default, TRILL automatically assigns
nicknames to RBs, and the priority for a RB
to hold a nickname is 64.
Configuring the link type of a TRILL port
The following link types are available for a TRILL port:
•Access—Access ports include access ports without the alone attribute and access ports with the
alone attribute. Access ports with the alone attribute do not send or receive Hello frames and do not
participate in DRB election or AVF negotiation. Access ports without the alone attribute can process
only local data frames and Hello frames.
•Hybrid—A hybrid port combines the attributes of an access port and a trunk port, and can process
local data frames and passing data frames.
•Trunk—A trunk port can process passing data frames and some of Layer 2 protocol frames (for
example, LLDP frames), but it cannot process local data frames.
•VR—A VR port is a virtual router port that can forward the following traffic:
{TRILL data frames.
{Layer 3 unicast data traffic.
{Layer 2 and Layer 3 multidestination data traffic.
Configuration restrictions and guidelines
•For the TRILL network to forward Layer 3 traffic, you must configure the link type as VR for TRILL ports
that are connected to an RB.
•VR ports are used only on P2P links, and both ends of a P2P link must be VR ports.
•A VR port trunks all VLANs. HP recommends that you reduce the number of announcing VLANs on
VR ports to reduce Hello frames.
Configuration procedure
To configure the link type of a TRILL port:

11
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter Layer 2 Ethernet
or aggregate
interface view.
interface interface-type
interface-number N/A
3. Configure the link
type of the TRILL port.
trill link-type { access [ alone ] |
hybrid |trunk | vr }
By default, the link type of a TRILL port is
access without the alone attribute.
Configuring the DRB priority of a TRILL port
On a broadcast network, TRILL must elect a DRB. An RB with a higher DRB priority is preferred in DRB
election. When two RBs have the same DRB priority, the RB with a higher MAC address takes
precedence.
To configure the DRB priority of a TRILL port:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter Layer 2 Ethernet or
aggregate interface
view.
interface interface-type
interface-number N/A
3. Configure the DRB
priority of the TRILL port. trill drb-priority priority By default, the DRB priority of a TRILL port is
64.
Configuring the link cost for a TRILL port
The link cost of a TRILL port can be automatically calculated by the system or manually configured.
•A manually configured link cost takes precedence over a calculated link cost.
•If no configured link cost exists and automatic link cost calculation is enabled, the calculated link
cost takes effect.
•If no configured link cost exists and automatic link cost calculation is disabled, the default link cost
of 2000 is used.
The system automatically calculates the link cost of a TRILL port by using the following formula: link cost
= 20000000000000/interface baud rate.
To configure the link cost for a TRILL port:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter TRILL view. trill N/A
3. Enable automatic link cost
calculation for TRILL ports. auto-cost enable
By default, automatic link cost
calculation is enabled for TRILL
ports.
4. Return to system view. quit N/A

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Step Command Remarks
5. Enter Layer 2 Ethernet
interface view or Layer 2
aggregate interface view.
interface interface-type
interface-number N/A
6. Configure the link cost for the
TRILL port. trill cost value The default setting is 2000.
Configuring announcing VLANs and the
designated VLAN
The concepts and symbols used to describe a VLAN on a port are as follows:
•Enabled VLAN—A VLAN enabled on the port.
•Forwarding VLAN—A VLAN for which the port is the appointed port.
•∩and ∪—Set operation symbols. ∩indicates set-theoretic intersection, and ∪indicates
set-theoretic union.
RBs send Hello frames in a set of VLANs. The VLAN set is calculated as follows:
•DRB—Enabled VLANs ∩(announcing VLANs ∪designated VLAN).
•Non-DRB—Enabled VLANs ∩(designated VLAN ∪(announcing VLANs ∩forwarding VLANs)).
To prevent Hello frames from consuming an excessive amount of CPU resources, reduce the number of
announcing VLANs.
RBs use the designated VLAN to forward TRILL protocol frames (except Hello frames) and local data
frames. For RBs to establish adjacencies and forward TRILL data frames, make sure the designated VLAN
is an enabled VLAN.
To configure announcing VLANs and the designated VLAN:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter Layer 2 Ethernet
interface view or Layer 2
aggregate interface view.
interface interface-type
interface-number N/A
3. Configure announcing
VLANs. trill announcing-vlan { vlan-list | null }
By default, no announcing VLAN is
configured, and announcing
VLANs are enabled VLANs.
4. Configure the designated
VLAN. trill designated-vlan vlan-id
By default, no designated VLAN is
configured. The system
automatically selects an enabled
VLAN as the designated VLAN.
Configuring TRILL timers
You can configure the following TRILL timers:

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•Hello interval and Hello multiplier—The RB advertises Hello frames at the Hello interval to maintain
a TRILL adjacency. The shorter the Hello interval, the faster the network convergence. However, a
shorter Hello interval consumes more system resources. The adjacency holding time is obtained by
multiplying the Hello interval by the Hello multiplier. The RB advertises the adjacency holding time
to neighbors through Hello frames. If a neighbor does not receive any Hello frame from the RB
within the adjacency holding time, it removes the TRILL adjacency with the RB.
•AVF inhibition time—As the AVF of a VLAN, the RB guarantees that frames of the VLAN enter and
leave a broadcast network through the same port. Other RBs on the broadcast network do not
process frames from the VLAN.
To avoid loops, the RB suppresses its AVF role during the inhibition time when one of the following
conditions exists:
{The RB detects a root bridge change on the broadcast network.
{Other RBs advertise a different AVF for the VLAN.
When the inhibition time expires, the RB restores its AVF role if it is still the AVF of the VLAN.
•CSNP interval—On a broadcast network, the RB advertises CSNPs at the CSNP interval to perform
network-wide LSDB synchronization if it is elected as the DRB. A CSNP records all LSP digests of the
RB's local LSDB. A remote RB compares a received CSNP against its local LSDB to verify whether
some LSPs are aged out or missing. If the CSNP has an LSP digest that the local LSDB does not have,
the remote RB sends a PSNP packet to request the LSP.
To configure TRILL timers:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter Layer 2 Ethernet
or aggregate interface
view.
interface interface-type
interface-number N/A
3. Configure the Hello
interval. trill timer hello interval
The default setting is 10 seconds.
This command sets the Hello interval for an
RB. The Hello interval of a DRB is 1/3 of the
Hello interval of an RB. This allows for DRB
failures to be quickly detected.
4. Configure the Hello
multiplier.
trill timer holding-multiplier
count The default setting is 3.
5. Configure the AVF
inhibition time. trill timer avf-inhibited time The default setting is 30 seconds.
6. Configure the CSNP
interval. trill timer csnp interval The default setting is 10 seconds.
Configuring TRILL LSP parameters and features
Setting TRILL LSP parameters
You can set the following LSP parameters:

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•LSP maximum age—The RB uses the LSP maximum age as the remaining lifetime of the LSPs that it
originates. When the RB detects that the remaining lifetime of an LSP reaches 0 seconds in the LSDB,
the RB performs the following tasks:
{Removes the LSP's content.
{Keeps the LSP's digest.
{Sets the LSP's remaining lifetime to 0 and purges the LSP from the network by advertising the LSP
to other RBs.
•LSP refresh interval—A locally originated LSP is forcibly refreshed when its remaining lifetime is no
greater than n: n = LSP maximum age – LSP refresh interval. This mechanism avoids frequent LSP
aging and ensures network stability.
•LSP generation timer parameters—By adjusting the TRILL LSP generation timer parameters, you can
prevent frequent network changes from consuming an excessive amount of bandwidth and device
resources.
When the network is stable, the LSP generation timer is set to the minimum interval for each LSP
generation. When the network is unstable, the LSP generation timer is added by the incremental
interval for each LSP generation until the maximum interval is reached.
•Maximum length of originated LSPs—The RB selects the smallest value from the following values as
the actual maximum length of LSPs to be sent to a neighbor:
{The configured maximum length of originated LSPs.
{The interface MTU.
{The maximum originated LSP length carried in the LSPs sent by the neighbor.
•Maximum length of received LSPs—When the RB receives an LSP that exceeds the length, the RB
drops the LSP.
•Overload bit of LSPs—The RB sets the Overload bit in LSPs if the RB fails and cannot correctly
perform route selection and packet forwarding. When the RB cannot record the complete LSDB
because of insufficient memory, routing calculation errors occur. To make troubleshooting easier,
temporarily exclude the RB from the TRILL network by setting the Overload bit for the LSPs sent by the
RB.
•Minimum LSP interval and maximum number of LSPs transmitted per interval—To avoid frequent
LSP aging in the network, RBs periodically advertise LSPs. The actual refresh interval of an LSP is
determined by both the minimum LSP interval and the maximum number of LSPs transmitted per
interval. To prevent LSPs from being aged out accidentally, set the LSP maximum age and the LSP
refresh interval appropriately.
To set TRILL LSP parameters:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter TRILL view. trill N/A
3. Set the LSP maximum
age. timer lsp-max-age time The default setting is 1200 seconds.
4. Set the LSP refresh
interval. timer lsp-refresh time The default setting is 900 seconds.

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Step Command Remarks
5. Set the TRILL LSP
generation timer
parameters.
timer lsp-generation
maximum-interval
[ minimum-interval
[ incremental-interval ] ]
By default, the maximum LSP generation
interval is 2 seconds, the minimum interval
is 10 milliseconds, and the incremental
interval is 20 milliseconds.
6. Configure the
maximum length of
originated LSPs.
lsp-length originate size
The default setting is 1458 bytes.
To prevent the system from generating error
messages, do not set the maximum length of
originated LSPs to be greater than the
maximum length of received LSPs.
7. Configure the
maximum length of
received LSPs.
lsp-length receive size
The default setting is 1492 bytes.
To prevent the system from generating error
messages, do not set the maximum length of
originated LSPs to be greater than the
maximum length of received LSPs.
8. Set the Overload bit of
LSPs and set the lifetime
for the set Overload bit.
set overload [ timeout ]
By default, the Overload bit is not set.
Do not perform this task on the root RB of a
TRILL distribution tree. The root RB cannot
forward traffic when the Overload bit of
LSPs is set on the RB.
9. Return to system view. quit N/A
10. Enter Layer 2 Ethernet
or aggregate interface
view.
interface interface-type
interface-number N/A
11. Configure the minimum
LSP interval and the
maximum number of
LSPs transmitted per
interval.
trill timer lsp interval [ count
count ]
By default, the minimum LSP interval is 10
milliseconds, and the maximum number of
LSPs transmitted per interval is 5.
Enabling TRILL LSP fast advertisement
LSP fast advertisement enables TRILL to immediately advertise the specified number of LSPs that invoke
SPF calculation. This mechanism improves network convergence time.
To enable TRILL LSP fast advertisement:
Ste
p
Command Remarks
1. Enter system view. system-view N/A
2. Enter TRILL view. trill N/A
3. Enable TRILL LSP
fast advertisement.
flash-flood [ flood-count flooding-count |
max-timer-interval flooding-interval ] *
By default, TRILL LSP fast
advertisement is disabled.

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Enabling TRILL pseudonode bypass
This feature disables a DRB from generating LSPs for the pseudonode when the DRB has only one
neighbor on a broadcast network. This reduces the number of LSPs in the network.
To enable the pseudonode bypass feature:
Ste
p
Command Remarks
1. Enter system view. system-view N/A
2. Enter Layer 2 Ethernet
interface view or Layer 2
aggregate interface view.
interface interface-type
interface-number N/A
3. Enable the pseudonode
bypass feature. trill bypass-pseudonode enable By default, the pseudonode bypass
feature is disabled.
Setting the SPF algorithm parameters
The RB uses the SPF algorithm to calculate a shortest path tree with itself as the root based on the LSDB.
The RB uses the shortest path tree to determine the next hop to a destination network. By adjusting the SPF
calculation intervals, you can prevent resource overconsumption when the network is unstable.
When the network is stable, the SPF calculation interval for continuous calculations is reduced to
minimum-interval. When the network is unstable, the SPF calculation interval is added by
incremental-interval × 2n-2 (n is the number of continuous SPF calculation times) for each SPF calculation
until the maximum interval is reached.
To set the SPF algorithm parameters:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter TRILL view. trill N/A
3. Set the SPF calculation
interval for TRILL.
timer spf maximum-interval
[ minimum-interval
[ incremental-interval ] ]
By default, the maximum SPF calculation
interval is 10 seconds, the minimum SPF
calculation interval is 10 milliseconds, and
the SPF calculation incremental interval is 20
milliseconds.
Configuring TRILL distribution trees
Setting basic distribution tree parameters
In a TRILL network, RBs perform the following tasks:
•Compute TRILL distribution trees according to the LSDB.
•Use the TRILL distribution trees to guide the forwarding of multidestination frames.
An RB with a higher priority is selected as the root bridge of a TRILL distribution tree.