Enabling IPv6 IS-IS MTR
On a network, IPv4 and IPv6 topologies must be consistent so that both IPv6 IS-IS and IPv4 IS-IS can use the SPF algorithm to perform route calculation. If they are different, routers supporting both IPv4 and IPv6 might send IPv6 packets to routers that do not support IPv6, resulting in packet loss.
To resolve this issue, configure IPv6 IS-IS Multi-Topology Routing (MTR) to perform route calculation separately in IPv4 and IPv6 topologies.
Figure 114: Network diagram
As shown in Figure 114, the numbers refer to the link costs. Router A, Router B, and Router D support both IPv4 and IPv6. Router C supports only IPv4 and cannot forward IPv6 packets.
Enable IPv6 IS-IS MTR on Router A, Router B, Router C, and Router D to make them perform route calculation separately in IPv4 and IPv6 topologies. With this configuration, Router A does not forward IPv6 packets destined to Router D through Router B, avoiding packet loss.
Configuration prerequisites
Before you configure IPv6 IS-IS MTR, configure basic IPv4 and IPv6 IS-IS functions, and establish IS-IS neighbors.
Configuration procedure
To enable IPv6 IS-IS MTR:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter IS-IS view. | isis [ process-id ] [ vpn-instance vpn-instance-name ] | N/A |
3. Specify an IS-IS cost style. | cost-style { wide | wide-compatible | compatible } | By default, the IS-IS cost style is narrow. |
4. Enter IPv6 address family view. | address-family ipv6 [ unicast ] | N/A |
5. Enable IPv6 IS-IS MTR. | multi-topology [ compatible ] | By default, IPv6 IS-IS MTR is disabled. |