It will be easier to look into this issue if you can provide the detail like where this router sits exactly. Like between P--P, PE--P, PE--PE. I believe that if packets are passing out from this interface and being labeled on the device very first time you need to set ip mtu too. In Cisco mpls mtu command only work for labeled packets.
Second if there are some gre tunnels involved along with mpls thn you may need to further tweak mtu settings. Regards, Masood Ahmad Shah -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Eric Kagan Sent: Friday, January 11, 2008 7:51 PM To: [email protected] Subject: [c-nsp] TCP Throughput / MTU problem ? with Cisco 7304 and MPLS VPN's I am running in to a strange problem and hopfeully someone here can help. I did open a Cisco TAC case but I don't think they understand the issue or maybe I didn't explain it well. We have MPLS enabled through the core of our network for customer MPLS VPN's. Until now, all devices have been 7206VXR's w/ NPE-G1's and we are only using the 3 internal Gig ports on the Processor. I upgraded one of the VXR's to a 7304 and configured it the same as the 7206. The router itself is working fine, BGP is working, regular IP traffic / throughout is fine (iperf tests have no issues). I have confirmed interface MTU's, switch MTU's and everything is configured the same as before. When VPN traffic goes through this link, I get reports of TCP requests starting and then stopping (i.e. SSH makes connection but can't pass data, or do an 'ls', etc or HTTP Get seems to connect but doesn't pass data back). It all sounds very similar to MTU issues I experienced and read about on MPLS interfaces. If I reroute the traffic around the ring away from the 7304 everything works fine again - and the problem connections are resolved in seconds. I originally had the MTU set to 1546 on the 7304 (I used to use 1524 but some of the L2 VPN's needed more so I bumped them up). I came across the document MPLS MTU Command Changes (http://www.cisco.com/en/US/products/ps6566/products_feature_guide09186a0080 629db0.html) which I found interesting so I set the MPLS MTU to 1520 with no avail. Below is show ver and config clips along with a few show commands. I am hoping someone has seen this and knows how to resolve. Thanks Eric Cisco IOS Software, 7300 Software (C7300-K91P-M), Version 12.2(31)SB6, RELEASE SOFTWARE (fc1) System image file is "disk0:c7300-k91p-mz.122-31.SB6.bin" cisco 7300 (NPEG100) processor (revision B) with 983040K/65536K bytes of memory. mpls label protocol ldp ! interface Loopback0 ip address 10.11.12.214 255.255.255.255 ! interface GigabitEthernet0 desc Backbone Switch ip address 10.11.13..1 255.255.255.224 ip flow ingress load-interval 30 media-type rj45 speed auto duplex auto negotiation auto mpls mtu 1520 mpls label protocol ldp mpls ip ! interface GigabitEthernet1 description Fiber to POP1 ip address 10.11.14.26 255.255.255.252 ip flow ingress load-interval 30 delay 10000 media-type gbic speed auto duplex auto negotiation auto mpls mtu 1520 mpls label protocol ldp mpls ip ! interface GigabitEthernet2 description Backbone Failover bandwidth 50 ip address 10.11.14.253 255.255.255.248 ip flow ingress load-interval 30 media-type rj45 speed auto duplex auto negotiation auto mpls mtu 1520 mpls label protocol ldp mpls ip ! router bgp xxxxx no synchronization bgp log-neighbor-changes neighbor RR_SERVER peer-group neighbor RR_SERVER remote-as xxxxx neighbor RR_SERVER update-source Loopback0 neighbor RR_SERVER next-hop-self neighbor RR_SERVER send-community both neighbor 10.11.12.201 peer-group RR_SERVER neighbor 10.11.12.201 description pecore-mma neighbor 10.11.12.203 peer-group RR_SERVER neighbor 10.11.12.203 description pecore-wma no auto-summary ! #show mpls int Interface IP Tunnel BGP Static Operational GigabitEthernet0 Yes (ldp) No No No Yes GigabitEthernet1 Yes (ldp) No No No Yes GigabitEthernet2 Yes (ldp) No No No Yes #show mpls ldp disc Local LDP Identifier: 10.11.12.214:0 Discovery Sources: Interfaces: GigabitEthernet0 (ldp): xmit/recv LDP Id: 10.11.12.216:0 LDP Id: 10.11.12.215:0 LDP Id: 10.11.12.217:0 GigabitEthernet1 (ldp): xmit/recv LDP Id: 10.11.12.203:0 GigabitEthernet2 (ldp): xmit/recv LDP Id: 10.11.12.215:0 LDP Id: 10.11.12.217:0 LDP Id: 10.11.12.216:0 Also, show mpls ldp binding and show mpls ldp nei show all the proper info. I sent an update back to Cisco on the TAC case but think someone here may understand and help quicker. Any help or insight would be appreciated. Thanks Eric Eric Kagan _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
