forwarding does not work if "label-allocation-mode per-vrf" is not set using BVI interfaces
Appreciate your helps making me understand the use of the following command:
The issue I have is that without that command configured under the vrf under the bgp process, forwarding to destinations configured under static routing as the pe-ce vrf routing does not work.
Once I enable that command, forwarding starts working. I want to understand why? and what change I can see in the LFIB or cef table if that command is set or not set??
I tryed looking at the mpls labels assigned to the destinations under vrf (with and without the command configured), I can see labels are always assigned, so apparently no difference there.
The routers is an ASR9k (IOS XR) router with BVI interface facing the CE side attached to a vrf "test", and TENG 0/0/0/0 attached to the mpls core.
In the vrf "test" static routing is configured to reach customer routes by a next-hop. As a BVI interface is configured, it is the outbound interface to route/reach the next hop and destination networks.
The change you should be able to observe is that if you create a second route, for example 192.168.200.66/32. It will be allocated the same label as the .65/32 prefix. When using per-prefix label allocation mode the label for each prefix would be unique.
You should be able to verify this with "show mpls forwarding vrf Ga" after adding an additonal route.
I came across this forums from a link provided from the CLI analyzer version 3.0 system diagnostics on our ASR9k network. We are running just a couple of VRFs default, MGMT, and a VOICE VRF that is in MP-BGP / L3VPN. We also have some ME3600 boxes in the network.
We are not having any issues running per-prefix allocation mode (default on both the 9k and ME3600).
We are running 5.1.3 on our 9k network, and a mix of 15.2.4.S1 and 15.4.3.S4 on our ME3600 boxes. Looks like per-vrf labels are not supported on 15.2.4.S1 as the command is not available. The command is also unavailable on 5.1.3 on the 9k.
I'm just trying to understand what per-vrf labels buys us and what to look out for if we do have a traffic loss issue. We already found a bug in 15.4.3.S4 where random IP addresses are blackholed when the interface is configured as a trunk (workaround is to use service instance).
In my understanding the per-vrf label method is meant to save resource on a PE devices on label allocation. Imagine there is a PE devices with only a few VPN but a lot of local prefixes, under per-VRF label allocation this device would use less memory?
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