Unanswered Question
Jul 7th, 2010
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Below is the description of the problem.

I've tried deleting all sub-interfaces on  the Juniper and tried re-adding one at a time. Sometimes it keeps the high CPU  on the switches (As we start seeing VRRP mac flaps as if something goes into a  loop) and other times it's fine,  but what is consistent is the  following:

We have a MGT vlan 2 ,   which is a L3VPN on the Juniper's  .  This is obviously carried on the Trunk ports between  the 2 Cisco Switches.  When I allow all vlan's on the Uplink Trunk ports on the  Cisco  to the Juniper and bring up Vlan 2 ,  I get packet loss and slow SSH  response to the 2 switches( CPU remains normal on the Cisco Switches i.e around  11%) on this MGT vlan .  If I only allow vlan 2 on the Trunk/Port channel up to  LONIR2(MX960) ,  It's fine.  I don't get packet loss or slow SSH,telnet etc etc  response times.  This only happens on the link between Cisco switch BRIIS2   (4948) and LONIR2(MX960). This is an issue occuring on 2 sites we currently  have.  The only common factor is that Virgin/NTL provide the tail circuit and  that it goes through our LONIR2 router. 

The packet loss and slow response I experience is when I’m  coming from  our MGT server that resides behind a MGT VPN .  This VPN is overlapped with this  MGT VPN to get to the Bristol site .

We currently have 16 sites with the same setup ,  some have LACP enabled  on the links(as some of the Telco carriers don't provide Link Loss forwarding)  and some we have not enabled.  On the sites this is occuring on , the one has  LACP enabled and the other does not,  so I don't believe this has anything to do  with traffic across the LACP link.

When testing all hops along the way I don’t get any packet loss or slow  response ,  it’s only end-to-end.

We've now run packet captures on both ends of the link and noticed  No  PVST+ information is coming across from the Bristol end.

Any suggestion are more than welcome

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