Huawei BFD configuration specification

BFD Configuration specifications for
BFD for LSP The round-trip path of the session message needs to be consistent to ensure LSP Normal path switching
To configure BFD for LSP During session detection , From source device to destination device LSP Path and return LSP perhaps IP The path is inconsistent . Return trip LSP perhaps IP When the path fails , BFD conversation Down , Lead to LSP Path MIS cut

in .

Application scenarios
Pictured Shown , RouterA And RouterB There are two paths between , route 1 And the path 2 .

BFD for LSP Inconsistent round-trip paths of session messages lead to LSP Network diagram of path error switching

NE Router -BFD Configuration specifications for -4812357-1

Configuration specification
Deploy on the network BFD for LSP During session detection ：

1. dynamic BFD for LSP conversation , Consider configuring routing constraints , Ensure that the back and forth paths are consistent , For example, use high priority static routing .

2. static state BFD for LSP conversation （ barring BFD for TE-LSP）, Consider configuring routing constraints , Ensure that the back and forth paths are consistent , For example, use high priority static routing .

3. static state BFD for TE-LSP conversation , Through strict explicit path constraints LSP Back and forth path , And the diameter of the incoming circuit is configured BFD for TE-LSP Type session , Ensure that the back and forth paths are consistent .

The risk of non-standard configuration
Risk description

1. Configuration dynamics BFD for LSP Session detection , The way to go 1 by LSP route , Return path 2 by IP route .

2. Configure static BFD for LSP conversation （ barring BFD for TE-LSP）, Return path 2 by LSP route , And with the RouterA To RouterB Of LSP Paths do not share paths .

3. route 1 And the path 2 All configured BFD for TE-LSP conversation ,RouterA and RouterB Of course TE-LSP There is no strict explicit path configured .

When any of the above conditions is met ,BFD The outgoing and return paths of the session are inconsistent , When the return path fails , It may lead to the journey LSP Wrong path switching .

The business phenomenon is as follows ：

BFD The conversation is intended to detect the path 1, But when the path 2 When it breaks down , because BFD The return path is blocked , conversation Down, Trigger path 1 Upper LSP Switch to the fault path by mistake 2 On , This leads to the loss of business traffic .

Risk judgment method

1. Let's take a dynamic BFD The process of conversation is LSP route , The return journey is IP Routing as an example . The judgment method of other situations should be determined according to the actual networking situation , It must be ensured that BFD The outgoing and return paths of the session message are consistent .

2. stay RouterA Inquire about BFD Session neighbor information .

# In the user view , perform display bfd session all verbose Command view RouterA To RouterB Of BFD Neighborhood information . Bold font is RouterA To RouterB Of BFD Conversation neighbors and next hop .

display bfd session all verbose

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State : Up Name : dyn_16396

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Local Discriminator : 16396 Remote Discriminator : 16392

Session Detect Mode : Asynchronous Mode Without Echo Function

BFD Bind Type : TE_LSP

Bind Session Type : Dynamic

Bind Peer IP Address : 10.2.2.2

NextHop Ip Address : 10.1.1.2 …

3. stay RouterB Inquire about BFD Neighbor information of the session .

# In the user view , perform display bfd session all verbose Command view RouterB To RouterA Of BFD Neighborhood information . Bold font is RouterB To RouterA Of BFD Conversation neighbors .

display bfd session all verbose

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(Multi Hop) State : Up Name : dyn_16392

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Local Discriminator : 16392 Remote Discriminator : 16396

Session Detect Mode : Asynchronous Mode Without Echo Function

BFD Bind Type : Peer IP Address

Bind Session Type : Entire_Dynamic

Bind Peer IP Address : 10.1.1.1

…

4. stay RouterB Query to RouterA Routing information for .

In the user view , perform display ip routing table ip address mask verbose Command query RouterB To RouterA Routing information for . Bold font is RouterB To RouterA The next hop of the route .BFD Session from RouterA To RouterB My next jump is 10.1.1.2 , And from RouterB To RouterA My next jump is 10.2.1.2 BFD The round-trip path of the session message is inconsistent .

display ip routing-table 10.1.1.1 32 verbose

Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route

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Routing Table : public

Summary Count : 1

Destination: 10.1.1.1/32

Protocol: ISIS-L2 Process ID: 1

Preference: 15 Cost: 10

NextHop: 10.2.1.2 Neighbour: 0.0.0.0

State: Inactive Adv Age: 1d04h15m09s

Tag: 0 Priority: high

Label: NULL QoSInfo: 0x0

IndirectID: 0xE600087A

RelayNextHop: 0.0.0.0 Interface: GigabitEthernet0/5/5

TunnelID: 0x0 Flags:

Risk recovery plan
Please configure according to the configuration specification .