MAC address learning

[cloughy1]

Hi, new to the alcatel stuff. I work for a service provider, typically we would have a 6250 at a customer site which connects into an Alcatel SR, maybe a 7450 or 7750 which then traverses our network to the other side where it will exit another 7450 onto the customer's other site 6250.

Site A 6250----7450/7750-----network-------7450-----6250 Site B

We get a number of faults where one or both 6250's haven't learnt MAC addresses. Could be a uni-directional thing or bi-directional.

I am trying to get my head around the mac learning process here. What MAC's should be learnt? Customer kit plugged into the 6250's? How are the addresses learnt? What issues could cause them not to be learnt? Any general issues around this area, would be great to hear from someone. How do we see MAC info on the SR itself?

Also any commands to help troubleshoot this would be great.

[humbertoss]

Hi cloughy1,

What kind of service do you are using on 7750?
If you are using VPRN the behavior MAC learning is different that VPLS services.
Please, explain better your services.

[mivens]

If it's an epipe, there is no MAC learning.

For a VPLS service, the command is

show service id <service-id> fdb detail

[satishgawli]

IN EPIPE services

how can we know whether link is UP as we cannot see mac address from both end . in cisco we can see mac learning from customer end interface (downlink)and uplink from MPLS cloud which mac of distant end device. If switch is connected to ALU PE then we can see on switch but if link is directly on PE then how to check.

[satishgawli]

IN epipe service

there is no mac learning then how can we check link is up or down. from which end we are getting mac or which end not.

CE----PE----MPLS-----PE-----CE
<-----epipe------->

We can check on switch end but if link is terminated on routers itself then how to check from which end mac is learning or which end not.

[thekotaksampah]

like all people side, to verify this, you should check mac address in CE, but before do that, make sure you epipe clear from connection issue.

1. Make sure epipe service is up (sap up and spd up)
2. Make sure sap have matching vlan with customer if you using vlan to your customer

[mivens]

I don't believe there is MAC learning on a Cisco xconnect/pseudowire service either. It's the same point-to-point technology.

In terms of testing/verification you can also do an oam vccv ping from one 7750 to the other.

You may also be able to use the test-oam commands on the 6250s to generate some traffic end-to-end.

[Rickdatech]

Most service providers have switches on the edge, (at the handoff to the customer) there are some exceptions. Switches learn MAC addresses from the customer equipment. The 7450 and the 6250 are switches, the 7750 is a service router. They work differently.

Switches learn MAC addresses. When they receive an Ethernet frame, they look in their forwarding tables to see if they have received anything on that port from that MAC address, if not, they add the MAC address to their forwarding table. The MAC address will stay in the forwarding table for a set period of time, then it will be removed.

Your customer must see his MAC address through the provider's network.