MPLS TE IPv6 Autoroute
The MPLS TE IPv6 Autoroute feature enables the use of IPv4 MPLS TE tunnels for IPv6 routing. The routing
protocol IGP (IS-IS) considers the IPv4 MPLS TE tunnel for IPv6 routing path calculation only if the tunnel
is advertised to carry IPv6 traffic. To advertise the tunnel, either IPv6 autoroute announce (AA) configuration
or IPv6 forwarding adjacency (FA) configuration should be made on the tunnel. Also, the IPv6 has to be
enabled on the tunnel so that the tunnel can handle IPv6 traffic.
To configure IPv6 routing on an MPLS TEv4 tunnel, see Configuring IPv6 Routing Over IPv4 MPLS-TE
Tunnels, on page 334.
MPLS TE IPv6 Autoroute Restrictions
•
IGP support is only for IS-IS.
•
IS-IS IPv4 and IPv6 must be configured under the same IS-IS instance.
•
Unequal load balancing (UELB) does not apply to IPv6 traffic. While it may still be configured and
used for IPv4 traffic, IPv6 traffic does not acknowledge the UELB configuration. However, equal
loadsharing works for IPv6.
•
Policy-based tunnel selection (PBTS) does not apply for IPv6 traffic. While it may still be configured
and used for IPv4 traffic, IPv6 traffic does not acknowledge the PBTS configuration.
•
MPLS auto tunnels do not support IPv6 autoroute announce and IPv6 forwarding adjacency configurations.
MPLS TE Path Cost Limit
The MPLS TE path cost limit feature enables graceful migration of TE label switched paths (LSPs) away
from a link without affecting the traffic. This is useful when a link is scheduled to be decommissioned or
brought down for maintenance.
In order to take a link out of service and gracefully migrate the LSPs away from it, the cost assigned to the
link is to be set higher than the path cost limit (path aggregate admin-weight) assigned at the LSP headend.
The cost of the tunnel is equal to the aggregate cost of the links through which the tunnel passes. The headend
routers recalculate the total path costs at the time of periodic path verification. At this stage, the headend
routers automatically check if the path limit is crossed and reroute the LSPs away from the out-of-service
link.
Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router, Release 5.1.x
211
Implementing MPLS Traffic Engineering
MPLS TE IPv6 Autoroute
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