H3C SR6600 SPE-FWM Installation manual

H3C SR6600[SR6600-X] Routers
Segment Routing Command Reference
New H3C Technologies Co., Ltd.
http://www.h3c.com
Software version: SR6600_SR6600X-CMW710-R7809
Document version: 6W300-20200823

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contained herein.

Preface
This configuration guide describes segment routing fundamentals and configuration procedures.
This preface includes the following topics about the documentation:
•
Audience.
•
Conventions.
•
Documentation feedback.
Audience
This documentation is intended for:
•
Network planners.
•
Field technical support and servicing engineers.
•
Network administrators.
Conventions
The following information describes the conventions used in the documentation.
Command conventions
Convention
Description
Boldface Bold text represents commands and keywords that you enter literally as shown.
Italic Italic text represents arguments that you replace with actual values.
[ ] Square brackets enclose syntax choices (keywords or arguments) that are optional.
{ x | y | ... }
Braces enclose a set of required syntax choices separated by vertical bars, from which
you select one.
[ x | y | ... ]
Square brackets enclose a set of optional syntax choices separated by vertical bars,
from which you select one or none.
{ x | y | ... } *
Asterisk marked braces enclose a set of required syntax choices separated by vertical
bars, from which you select a minimum of one.
[ x | y | ... ] *
Asterisk marked square brackets enclose optional syntax choices separated by vertical
bars, from which you select one choice, multiple choices, or none.
&<1-n> The argument or keyword and argument combination before the ampersand (&) sign
can be entered 1 to n times.
# A line that starts with a pound (#) sign is comments.
GUI conventions
Convention
Description
Boldface Window names, button names, field names, and menu items are in Boldface. For
example, the New User window opens; click OK.
> Multi-level menus are separated by angle brackets. For example, File > Create >
Folder.

Symbols
Convention
Description
WARNING! An alert that calls attention to important information that if not understood or followed
can result in personal injury.
CAUTION:
An alert that calls attention to important information that if not understood or followed
can result in data loss, data corruption, or damage to hardware or software.
IMPORTANT:
An alert that calls attention to essential information.
NOTE:
An alert that contains additional or supplementary information.
TIP:
An alert that provides helpful information.
Network topology icons
Convention
Description
Represents a generic network device, such as a router, switch, or firewall.
Represents a routing-capable device, such as a router or Layer 3 switch.
Represents a generic switch, such as a Layer 2 or Layer 3 switch, or a router that
supports Layer 2 forwarding and other Layer 2 features.
Represents an access controller, a unified wired-WLAN module, or the access
controller engine on a unified wired-WLAN switch.
Represents an access point.
Represents a wireless terminator unit.
Represents a wireless terminator.
Represents a mesh access point.
Represents omnidirectional signals.
Represents directional signals.
Represents a security product, such as a firewall, UTM, multiservice security
gateway, or load balancing device.
Represents a security module, such as a firewall, load balancing, NetStream, SSL
VPN, IPS, or ACG module.
Examples provided in this document
Examples in this document might use devices that differ from your device in hardware model,
configuration, or software version. It is normal that the port numbers, sample output, screenshots,
and other information in the examples differ from what you have on your device.
T
T
T
T

Documentation feedback
You can e-mail your comments about product documentation to [e-mail].
We appreciate your comments.

i
Contents
Configuring MPLS SR····················································································1
About MPLS SR·················································································································································1
MPLS SR characteristics ···························································································································1
Basic concepts···········································································································································1
How MPLS SR works·································································································································1
Static segment configuration······················································································································2
Dynamic SID allocation······························································································································2
Label forwarding entry installation based on SIDs·····················································································2
SRLSP setup··············································································································································3
Packet forwarding in MPLS SR··················································································································4
MPLS SR and LDP interworking················································································································6
Protocols and standards ····························································································································7
MPLS SR tasks at a glance·······························································································································7
IP traffic forwarding over SRLSPs tasks at a glance··················································································7
MPLS TE traffic forwarding over static SRLSPs tasks at a glance····························································7
Configuring static segments·······························································································································8
Prerequisites··············································································································································8
Configuring a static adjacency segment ····································································································8
Configuring a static prefix segment············································································································9
Configuring IGP-based SID advertisement········································································································9
IGP-based SID advertisement tasks at a glance ·······················································································9
Configuring the IGP to support MPLS SR··································································································9
Configuring prefix SIDs····························································································································10
Enabling MPLS SR adjacency label allocation for the IGP······································································11
Configuring the MPLS SRGB···················································································································11
Configuring the device to prefer SRLSPs in traffic forwarding·········································································12
Configuring an MPLS TE tunnel to use static SRLSPs····················································································13
Tasks at a glance·····································································································································13
Configuring a static SRLSP······················································································································13
Binding a static SRLSP to an MPLS TE tunnel interface·········································································13
Display and maintenance commands for MPLS SR························································································14
MPLS SR configuration examples ···················································································································14
Example: Configuring MPLS SR based on static segments····································································14
Example: Configuring MPLS SR based on ISIS-advertised SIDs····························································20
Example: Configuring MPLS SR based on OSPF-advertised SIDs·························································27
Example: Configuring MPLS SR and LDP interworking···········································································34

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Configuring MPLS SR
About MPLS SR
Segment Routing (SR) is a source routing technology. The source node selects a path for the
packets, and then encodes the path in the packet header as an ordered list of segments. Each
segment is identified by the segment identifier (SID). The SR nodes along the path forward the
packets based on the SIDs in the packets. Only the source node needs to maintain the path status.
SR can operate with MPLS. In an MPLS network, SR uses MPLS labels as SIDs to forward packets
on an LSP.
MPLS SR characteristics
MPLS SR has the following characteristics:
•
MPLS SR forwards packets based on the existing MPLS infrastructure. No infrastructure
modifications are needed to implement SR on an MPLS network. For more information about
the MPLS infrastructure, see MPLS basics configuration in MPLS Configuration Guide.
•
MPLS SR expands and optimizes existing IGPs and uses the IGPs to distribute labels.
•
MPLS SR implements network features such as MPLS TE in a simpler way, eliminating issues
such as heavy and complicated routing protocol deployment.
Basic concepts
•
SR node—A node enabled with the MPLS SR feature. The ingress node (source node) adds
labels to packets. The transit nodes forward packets based on labels. The egress node
removes labels and forwards packets to the destination networks. SR nodes form an SR
domain.
•
Segment—An instruction an SR node executes on the incoming packet.
•
SID—Segment ID, which is MPLS label in MPLS SR.
•
Segment type—The following types of segments are available:
Prefix segment—SIDs are assigned to nodes based on destination address prefix. The
nodes create prefix-specific forwarding entries.
Adjacency segment—SIDs are assigned to nodes based on adjacency.
•
SRLSP—Segment routing label switched path, an LSP along which SR uses MPLS labels as
SIDs to forward packets.
•
SRGB—Segment routing global block, a range of global labels dedicated for MPLS SR prefix
SIDs. Different nodes can have different SRGBs. The minimum label value of an SRGB label
range is referred to as the base value of the SRGB. Labels 16000 through 24000 are reserved
for SRGBs.
How MPLS SR works
MPLS SR involves the following steps:
1. Label allocation for all nodes and links along the packet forwarding paths.
The following methods are available:
Static segment configuration
Dynamic SID allocation

2
2. Label forwarding entry installation based on SIDs. All MPLS SR devices in the SR domain use
the allocated labels to create label forwarding entries.
3. SRLSP setup. You can manually configure SRLSPs, or use an IGP or a controller to
dynamically create SRLSPs.
When the ingress node of an SRLSP receives a packet, it adds labels to the packet and forwards the
packet to the egress node through the SRLSP. After receiving a packet from the SRLSP, the egress
node removes the label and forwards the packet based on the routing table.
You can bind a higher layer application (for example, MPLS TE) to an SRLSP to forward traffic of the
application through the SRLSP.
Static segment configuration
Static MPLS SR provides the following methods for configuring static segments for a destination:
•
Prefix segment method—Manually configure the incoming label, outgoing label, and next hop
for the destination address prefix on each SR node.
•
Adjacency segment method—Manually configure the incoming label and next hop for the
adjacency to the neighbor on each SR node.
Dynamic SID allocation
MPLS SR expands IGP protocols such as IS-IS and OSPF to advertise SIDs in IGPprotocol packets.
MPLS SR provides the following methods for dynamically allocating and advertising SIDs:
•
Prefix SID—After you configure an SID for the loopback address on each SR node, the SIDs
uniquely identify the SR nodes. All SR nodes in the SR domain use an IGP to advertise their
own prefix SIDs. After receiving advertised prefix SIDs, each SR node calculates the prefix
SIDs to the advertisers.
The prefix SID advertisement can be one of the following types:
Absolute value advertisement—Each SR node advertises the prefix SID absolute value
and the SRGB.
Index value advertisement—Each SR node advertises the prefix SID index and the
SRGB.
Each SR node is assigned a globallyunique index value for the node's prefix. The prefix SID
an SR node allocates for a prefix equals the SRBG base of the SR node plus the index for
that prefix.
NOTE:
The device supports only the index value advertisement in the current software release.
•
Adjacency SID—Each SR node with adjacency SID allocation enabled allocates SIDs for the
IGP adjacencies (that is, the links to its IGP neighbors), and uses the SIDs to identify the links.
Label forwarding entry installation based on SIDs
Label forwarding entry installation based on prefix SIDs
Label forwarding entries based on prefix SIDs can be static or dynamic.
•
Static label forwarding entries—The device creates local label forwarding entries based on
manually configured incoming labels, outgoing labels, and next hops.
•
Dynamic label forwarding entries—The device uses the IGP to flood in the SR domain the
local SRGB and the index of the prefix SID for the local loopback interface. Based on the

3
flooded information, the other devices in the domain calculates their local label forwarding
entries by using the following rules:
Incoming label = Local SRGB base value + Index
Outgoing label = SRGB base value of the next hop + Index
Figure 1 Creating label forwarding entries based on prefix SIDs
Figure 1 shows how dynamic label forwarding entries are created. After you assign index value 201
to loopback address 1.1.1.1/32 on Device C, Device C uses an IGP packet to advertise the index
value and its local SRGB. Then, the devices calculate incoming and outgoing labels according to the
previously mentioned label calculation rules.
•
Devices C calculates its incoming label, which is 18201.
•
Device B calculates its incoming label and outgoing label and creates a label forwarding entry.
The incoming label is 17201. The outgoing label is 18201. The next hop is Device C.
•
Device A calculates its incoming label and outgoing label and creates a label forwarding entry.
The incoming label is 16201. The outgoing label is 17201. The next hop is Device B.
Label forwarding entry installation based on adjacency SIDs
When using adjacency SIDs, each device allocates a static or dynamic incoming label to the link to
its neighbor. The label has local significance. Multiple devices can use the same adjacency SID.
Figure 2 Creating label forwarding entries based on adjacency SIDs
As shown in Figure 2, the devices are running the same IGP. After IGP adjacencies are established
between the devices, Device A, Device B, and Device C allocates labels and creates label
forwarding entries as follows:
•
Device A allocates label 203 to the link to its neighbor Device B.
•
Device B allocates label 202 to the link to its neighbor Device C.
•
Device C allocates label 201 to the link to its neighbor Device D.
•
Device A creates a label forwarding entry with incoming label 203 and next hop Device B.
•
Device B creates a label forwarding entry with incoming label 202 and next hop Device C.
•
Device C creates a label forwarding entry with incoming label 201 and next hop Device D.
SRLSP setup
You can use the following methods to create SRLSPs:
•
Manually configure an SRLSP.
Device A Device B Device C
1000
Range
SRGB Base
16000 1000
Range
SRGB Base
17000 1000
Range
SRGB Base
18000
L
o
o
p
0
1
.
1
.
1
.
1
/
3
2
201
Device B
Nexthop
In Label
16201 Out Label
17201 Device C
Nexthop
In Label
17201 Out Label
18201 In Label
18201
Device A Device B Device C
Device B
NexthopIn Label
203 Device C
Nexthop
In Label
202 Device D
Nexthop
In Label
201
Device D

4
To configure an SRLSP, you must specify the label stack for packets to be forwarded along the
SRLSP on the ingress node. Each label in the stack corresponds to a prefix SID or adjacency
SID. The system can look for the outgoing label and next hop based on the prefix SID or
adjacency SID.
•
Configure SR nodes to use an IGP to dynamically establish an SRLSP.
SR nodes follow these steps to establish SRLSPs:
a. Use an IGP to collect prefix SID information from the MPLS SR network.
b. Calculate the shortest paths to other SR nodes based on the collected prefix SID
information and the IGP network topology.
c. Establish SRLSPs based on the shortest paths.
•
Configure a controller to deploy SRLSP configuration to the device so the device creates
SRLSPs.
For more information about controller configuration, see the user guide for the controller.
Packet forwarding in MPLS SR
Based on the SID allocation method, MPLS SR uses one of the following packet forwarding
methods:
•
Prefix SID-based packet forwarding—The ingress node encapsulates the prefix SID for the
egress node to a packet. The transit nodes forward the packet based on label forwarding
entries.
•
Adjacency SID-based packet forwarding—The ingress node encapsulates the label stack
that contains the adjacency SIDs of all links along the forwarding path to a packet. Each transit
node uses the top label in the label stack to determine the next hop and pops the top label
before forwarding the packet to the next hop.
•
Prefix and adjacency SID-based packet forwarding—The nodes use prefix SID-based
packet forwarding in combination with adjacency-based packet forwarding.
Prefix SID-based packet forwarding
Figure 3 shows how a packet is forwarded along the SRLSP from Device A to Device E based on
prefix SIDs. In this example, the outgoing label for the packet is 21201 on Device A.
1. Ingress node Device A searches for a forwarding entry for label 21201, adds outgoing label
20201 to the packet and sends the packet to the next hop (Device B).
2. When transit node Device B receives the packet, it searches for a label forwarding entry that
matches the label in the packet. Then, Device B uses the outgoing label of the matched entry
(19201) to replace the label in the packet and forwards the packet to the next hop (Device C).
3. Transit nodes Device C and Device D process the packet in the same way Device B does.
4. When egress node Device E receives the packet, it removes the label and forwards the packet
by IP address.
Figure 3 Prefix SID-based packet forwarding
Device A Device B Device C Device D Device E
Device B
NexthopIn Label
21201 Out Label
20201
Device C
NexthopIn Label
20201 Out Label
19201
Device D
NexthopIn Label
19201 Out Label
18201
Device E
Nexthop
In Label
18201 Out Label 17201
In Label
17201
20201
IP data 19201 IP data 18201 IP data 17201
IP data