BFD IPv6 Encapsulation Support
Bidirectional Forwarding Detection for IPv6 encapsulations are described within a session information structure. These session information structures are defined by BFDv6 for the protocols supported. BFDv6 uses information from the session information structures to determine the correct encapsulation for BFDv6 packets on that session.
Prerequisites for BFD IPv6 Encapsulation Support
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When using Bidirectional Forwarding Detection over IPv6 (BFDv6), IPv6 Cisco Express Forwarding and IPv6 unicast routing must be enabled on all participating routers.
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When you configure BFD IPv6 software sessions, you should configure the following CLI command:
no ipv6 nd nud igp
Restrictions for BFD IPv6 Encapsulation Support
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BFDv6 supports only global IPv6 neighbor addresses if a global IPv6 address is configured on the interface.
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Only asynchronous mode is supported. In asynchronous mode, either BFDv6 peer can initiate a BFDv6 session.
Information About BFD IPv6 Encapsulation Support
Overview of the BFDv6 Protocol
This section describes the BFDv6 protocol, how it is different from BFD for IPv4, and how it works with BFD for IPv4. BFD is a detection protocol designed to provide fast forwarding path failure detection times for all media types, encapsulations, topologies, and routing protocols. In addition to fast forwarding path failure detection, BFD provides a consistent failure detection method for network administrators. BFDv6 provides IPv6 support by accommodating IPv6 addresses and provides the ability to create BFDv6 sessions.
BFDv6 Registration
BFD clients register with BFD using a registry application program interface (API). The registry arguments include protocol type and the address and interface description block (IDB) of the route to be monitored. These APIs and arguments are all assumed by BFD to be IPv4.
BFDv6 has registries from which these arguments have been removed, and the protocol and encapsulation are described within a session information structure. These session information structures are defined by BFDv6 for the protocols supported. BFDv6 uses information from the session information structures to determine the correct encapsulation for BFDv6 packets on that session.
BFDv6 Global and Link-Local Addresses
BFDv6 supports both global and link-local IPv6 addresses for neighbor creation. BFDv6 sessions select source addresses to match the neighbor address types (for example, global IPv6 address neighbors must be paired with global IPv6 source addresses and link-local IPv6 address neighbors must be paired with link-local IPv6 source addresses). The table below shows the address pairings that BFDv6 supports.
Source Address |
Destination Address |
Status |
---|---|---|
Global |
Global |
Supported |
Global |
Link local |
Not supported |
Link local |
Global |
Not supported |
Link local |
Link local |
Supported |
Because all IPv6-enabled interfaces have a link-local address and BFDv6 selects the source address, link-local address neighbors are always paired with a link-local interface address. The link-local source address with global destination address is not supported by Cisco Express Forwarding. Therefore, a global IPv6 address must be configured on an interface before a session with a global address neighbor may be established in BFDv6. BFDv6 rejects any sessions in which the neighbor address is global and no global address is configured on the interface.
Note |
The behavior of a unique local address (ULA) in BFDv6 is the same as a global address. |
BFD for IPv4 and IPv6 on the Same Interface
BFD supports multiple IPv4 and IPv6 sessions per interface, with no restriction on the protocol of those sessions.
How to Configure BFD IPv6 Encapsulation Support
Configuring Baseline BFD Session Parameters on the Interface
Repeat this task for each interface over which you want to run BFD sessions to BFD neighbors.
SUMMARY STEPS
- enable
- configure terminal
- interface type number
- bfd interval milliseconds min_rx milliseconds multiplier interval-multiplier
DETAILED STEPS
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
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Enables privileged EXEC mode.
|
Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
interface type number Example:
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Specifies an interface type and number, and places the device in interface configuration mode. |
Step 4 |
bfd interval milliseconds min_rx milliseconds multiplier interval-multiplier Example:
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Enables BFD on the interface. |
Configuration Examples for BFD IPv6 Encapsulation Support
Example: Configuring BFD Session Parameters on the Interface
Device#show ipv6 ospf neighbor detail
Neighbor 172.16.4.4
In the area 0 via interface POS4/0
Neighbor: interface-id 14, link-local address FE80::205:5FFF:FED3:5406
Neighbor priority is 1, State is FULL, 6 state changes
Options is 0x63AD1B0D
Dead timer due in 00:00:33
Neighbor is up for 00:48:56
Index 1/1/1, retransmission queue length 0, number of retransmission 1
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 1, maximum is 1
Last retransmission scan time is 0 msec, maximum is 0 msec
Neighbor 172.16.3.3
In the area 1 via interface FastEthernet0/0
Neighbor: interface-id 3, link-local address FE80::205:5FFF:FED3:5808
Neighbor priority is 1, State is FULL, 6 state changes
DR is 172.16.6.6 BDR is 172.16.3.3
Options is 0x63F813E9
Dead timer due in 00:00:33
Neighbor is up for 00:09:00
Index 1/1/2, retransmission queue length 0, number of retransmission 2
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 1, maximum is 2
Last retransmission scan time is 0 msec, maximum is 0 msec
Neighbor 172.16.5.5
In the area 2 via interface ATM3/0
Neighbor: interface-id 13, link-local address FE80::205:5FFF:FED3:6006
Neighbor priority is 1, State is FULL, 6 state changes
Options is 0x63F7D249
Dead timer due in 00:00:38
Neighbor is up for 00:10:01
Index 1/1/3, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
Additional References for BFD IPv6 Encapsulation Support
Standards and RFCs
Standard/RFC |
Title |
---|---|
RFCs for IPv6 |
IPv6 RFCs |
Feature Information for BFD IPv6 Encapsulation Support
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Feature Name |
Releases |
Feature Information |
---|---|---|
BFD IPv6 Encapsulation Support |
Cisco IOS XE Everest 16.6.2 |
BFDv6 encapsulations are described within a session information structure. These session information structures are defined by BFDv6 for the protocols supported. BFDv6 uses information from the session information structures to determine the correct encapsulation for BFDv6 packets on that session. In Cisco IOS XE Everest 16.6.2, this feature was implemented on Cisco Catalyst 9400 Series Switches. |