Unanswered Question
Apr 9th, 2008

we config mpls on SPA-1XOC12-POS pos sdh interface.

what different between hdlc or ppp on this interface.

is there any problem for mpls if config ppp or HDLC on this interface?

thank you!

I have this problem too.
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mheusing Thu, 04/10/2008 - 03:34


There should not be any problem with either PPP or HDLC enabled on the interface.

If MPLS is enabled, labeled packets will be encapsulated in your L2 frame, i.e. PPP or HDLC frame. Hence it is called frame-mode MPLS.

As long as both ends of your OC12 line are configured for the same L2 protocol and the interface is up/up, there is not remarkable difference between both protocols. Note, that the default is HDLC in Cisco routers, which therefore will not show up in your configuration. The L2 protocol in place will be visible in the output of "show interface".

Hope this helps! Please use the rating system.

Regards, Martin

flyjunli Fri, 06/06/2008 - 01:34

Hi Martin,

some guys said, because HDLC just use keeplive message to detect failure, if one side receive keep alive, it get up state, but other side may not receive keep alive, it get down state.

thank you!


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