Hey, I have a problem that i just can't resolve. I hope someone will be able to help.
Here's the situation. I have 2 client switches (Catalyst 2400) each connected on a separate border router (7200). Between the router is a L2TPv3 tunnel. When i test the connection (RFC 2544) i get the result i expect +/-90Mb/s as long as the packet size is smaller then 1518. Once the packet size is 1518 the cpu of one of the two routers gets to 100% and the throughput lowers to +/-30Mb/s after about 30 seconds. I tested the maximum MTU with a ping and found out it's at 1472. I tried to change the ip mtu and mss to correct values (even tried lower values) but it didn't help. When i sniff the connection i noticed the mss value isn't the value i put one the interface. The lowest value i have seen is 1460 (wich should be allright). When i enable ip pmtu, i get with wireshark and on the routers the ICMP messages. Here's the intresting part of the config without changes of the mtu and mss( i basicly tried every possible mtu and mss config): Router 1: --------- c7200-adventerprisek9-mz.124-4.T1.bin Cisco 7206VXR (NPE-G1) processor (revision B) with 229376K/32768K bytes of memory. l2tp-class L2L-L2TP authentication password XXX ! pseudowire-class L2L-PW encapsulation l2tpv3 protocol l2tpv3 L2L-L2TP ip local interface Loopback100 ! interface Loopback100 ip address 172.16.0.1 255.255.255.224 ! interface GigabitEthernet0/1.200 encapsulation dot1Q 200 ip address 192.168.1.1 255.255.255.0 ip ospf cost 1 ! interface GigabitEthernet0/1.300 encapsulation dot1Q 300 ip address 192.168.2.1 255.255.255.0 ip ospf cost 10 ! interface GigabitEthernet0/2.100 encapsulation dot1Q 100 no cdp enable xconnect 172.16.0.2 100 pw-class L2L-PW Router 2: --------- c7200-adventerprisek9-mz.124-4.T1.bin Cisco 7206VXR (NPE400) processor (revision A) with 491520K/32768K bytes of memory. l2tp-class L2L-L2TP authentication password XXX ! pseudowire-class L2L-PW encapsulation l2tpv3 protocol l2tpv3 L2L-L2TP ip local interface Loopback100 ! interface Loopback100 ip address 172.16.0.2 255.255.255.224 ! interface FastEthernet0/0.200 encapsulation dot1Q 200 ip address 192.168.1.2 255.255.255.0 ip ospf cost 1 ! interface FastEthernet0/0.300 encapsulation dot1Q 300 ip address 192.168.2.2 255.255.255.0 ip ospf cost 10 ! interface FastEthernet0/1.100 encapsulation dot1Q 100 no cdp enable xconnect 172.16.0.1 100 pw-class L2L-PW Is there a way too change the value of the mtu so that packets don't get fragmented (i assume fragmentation makes the cpu go to 100%) or make the tunnel larger (again so that packets don't get fragmented)? I still think its weird default packets don't get through the tunnel. I tested the same L2TPv3 on a POS connection and get perfect results. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
