MPLS over MLPPP on Pos interface

Hi All,

 

I have been strugle on troubleshooting a real scenario where i am terminating 4xSTM1 PoS interface between a PE and P, so we want to bundle all this interfaces to just appear as one and running MPLS on top of it. So the problem is that when i put all the traffic into this new created Multilink PPP Pos interface with MPLS,  below are the problems:

  1 - The ISIS start flapping (sometimes)
  2 - L2VPN doens't work and L3VPN sometimes work (maybe to the ISIS issues above).
  3 - Even when LDP is established and l2vpn xconnect is up, the traffic cannot reach the other CE.

 

PE Config

pe-01#sh run int multilink 1
Building configuration...

Current configuration : 288 bytes
!
interface Multilink1
 mtu 9000
 ip address 10.227.227.50 255.255.255.252
 ip router isis
 mpls ip
 mpls traffic-eng tunnels
 ppp multilink
 ppp multilink group 1
 isis authentication mode md5
 isis authentication key-chain ISIS
 isis hello-interval minimal
 isis csnp-interval 10
end

pe-01#sh run int pos5/0
Building configuration...

Current configuration : 563 bytes
!
interface POS5/1
 description == BACKHAUL LINK TO P-01 >>>> STM1 ==
 mtu 9000
 no ip address
 encapsulation ppp
 load-interval 30
 carrier-delay msec 50
 no snmp trap link-status
 mpls ip
 crc 32
 pos ais-shut
 pos framing sdh
 pos report lais
 pos report lrdi
 pos report pais
 pos report prdi
 pos scramble-atm
 pos delay triggers path 0
 ppp multilink
 ppp multilink group 1

P Config

p-01#sh run int multilink 1
Building configuration...

Current configuration : 298 bytes
!
interface Multilink1
 mtu 9000
 ip address 10.227.227.49 255.255.255.252
 ip router isis
 mpls ip
 mpls traffic-eng tunnels
 ppp multilink
 ppp multilink group 1
 isis authentication mode md5
 isis authentication key-chain ISIS
 isis hello-interval minimal
 isis csnp-interval 10
end

interface POS3/1
 description == BACKHAUL LINK TO  PE-01  STM1 ==
 mtu 9000
 no ip address
 encapsulation ppp
 load-interval 30
 carrier-delay msec 50
 mpls ip
 crc 32
 pos ais-shut
 pos framing sdh
 pos report lais
 pos report lrdi
 pos report pais
 pos report prdi
 pos scramble-atm
 pos delay triggers path 0
 ppp multilink
 ppp multilink group 1
end

Considering the above situation can you please help me on troubleshooting?

 

Kind Regards

SPInsider

Comments

  • Does the MLPPP work w/o MPLS?  Does MPLS work with only a single link in the bundle?  I'm assuming that you have 4 in the bundle and only show the config for the first on each side in your example.

    I've had a large number of issues with services over mlppp over the years, from QoS only seeing one of the bundled links to routing protocols periodically flapping over it, etc.  This is probably IOS and platform related though.

  • Speaking from my own experiences within our network (and not knowing if there is a specific design goal with MLPPP over POS), use ECMP it's significantly less of a headache.  

    Was this previously working?  This is gonna sound stupid, but you haven't recently changed hostnames have you?  the hostname binds to the Multilink negotiation and can screw w/things when it doesn't refresh.

  • Hi pieces_of_eight,

     

    Yes the MLPPP is working w/o MPLS. MPLS is only work with physical interfaces, and not the bundle even with single link. I just post one interface since the other 3 are all the same, the only change is the interface pos x/y numbering.

    For this I am useing 7200-NPE-G2 and that is the code:

    pe-1#show version | in IOS
    Cisco IOS Software, 7200 Software (C7200P-ADVENTERPRISEK9-M), Version 12.4(15)T10, RELEASE SOFTWARE (fc3)
    BOOTLDR: Cisco IOS Software, 7200 Software (C7200P-BOOT-M), Version 12.4(15)T10, RELEASE SOFTWARE (fc3)

     

    Thanks

  • Dear Mud,

     

    The previous working and running at the moment is just on the physical link, we recently add more stm1 circuit onto that router. I didnt change hostnames recently.

    Can you share your experience with ECMP on this scenario?

     

    Thanks

  • I can't tell if you're saying the MLPPP config worked previously or just the physical links.  If the entire config previously worked, have you tried removing links from the multilink group one-by-one to see if a specific one is the cause of the issue?

    There isn't much to say on ECMP that isn't plainly obvious, in my experience it load balances traffic as well as MLPPP to the point where we no longer deploy it as a core facing solution.  We will still use MLPPP on customer facing T1s but (at least in our network) there isn't a real benefit to using MLPPP over ECMP. 

  • I'm assuming that the POS cards are standard POS-OC3 cards.  You've actually been able to bundle those ports with mlppp on a 7200 G2 w/o killing the cpu?  I'm impressed.  I would have thought CEF load sharing would be the best you'd be able to get from that box.

    Is ECMP even an option on 7200s?

  • I'm assuming that the POS cards are standard POS-OC3 cards.  You've actually been able to bundle those ports with mlppp on a 7200 G2 w/o killing the cpu?  I'm impressed.  I would have thought CEF load sharing would be the best you'd be able to get from that box.

    Is ECMP even an option on 7200s?

    You're totally right, I didn't see the post showing this was a 7200.  ECMP would torch a 7200, if it's even an option.  I think using CEF load sharing would be a better option than MLPPP though, but that's a personal opinion and I'm wrong a lot :)

  • Hi pieces_of_eight,

     

    I have achivied that by useing cef load-sharing, now i am monitoring the CPU utilization to check if it affect the perfomance.

     

    Thanks

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