MPLS only in one Direction

[Thomas Schmitt]

Hello

I just watched a strange thing - there is basic MPLS connection between PE1 <-> P <-> PE2 Router and I sniff outgoing messages from PE1 in this scenario. MPLS is enabled global with "ip cef" and also on all interfaces with "tag-switching ip" command - nothing else.

Now, If I ping from PE2 to PE1, then I didn't noticed any MPLS messages at all - for ICMP echo request messages is this ok, because (last) P-Router pops the label, but why there is no label on ICMP echo replay messages? If I send out some message from PE1, then is this message tagged, but not in case of replay message.

I'm a bit confused about it

thanks

[Ivan Krimmel]

Hi Dmytro.

please try to source pings from/to loopbacks.

[Nagendra Kumar Nainar]

Hi Dmytro,

When you trigger ping from PE2, it will be sent with source address as outgoing interface address which in this case will be the address on link connected between PE2 and P. This address will be advertised by P to PE1 with label 3 which means to pop.

So when PE1 replies, it sends without any label. This is expected.

As Ivan suggested, Can you try pinging between loopback address/. This will get you ICMP reply pkt with label imposed in your sniffer capture

HTH,

Nagendra