Passport latency?

[AyrishGrl]

I have a Passport 8600 and I have recently noticed spikes in response time to our Border routers. We have 2 7204s directly connected to our Passport. Both are in the same VLAN and are hardcoded to 100-full. Pings times from the passport to the routers spike as high at 180+ms at times. I see no errors on the Fast ethernet interfaces of the rotuers and the only thing on the passport ports that I see are InDiscards rising. Routers are connected to the passport with cat-5 cabling. I am wondering if this is contributing to some intermitant and mysterious latency issues I have been trying to track down.

The problem is I can't seem to pinpoint what is causing the high response times. Two different ports on the passport and two different cables are involved so I doubt those are suspect. Both router interfaces are hard coded to full duplex.

 

[Brat2]

Hi,
Have you checked Cisco routes utilization? Maybe problem is on this side? Check CPU load etc. Of cource You can reconfigure Passport 8600 VLAN's and use other ports on Nortel's side.

Brat

 

[AyrishGrl]

Utilization on both sides are low. Passport is at 10% CPU overall and the port runs around 10-20mbps. I am running two networks on the same interface on the Cisco that is coming into the passport. There are no VLANs on the router, so I essentially have two networks coming into 1 VLAN on passport. Both Cisco and Nortel have suggested configuring two separate VLANs for the networks on all equipment involved (routers, passport and Pix FW). Looks like it is going to be a long weekend.

 

[netmanrick]

Did Nortel or Cisco mention anything anout MTU mismatch ?

Rick Harris
SC Dept of Motor Vehicles
Network Operations

 

[AyrishGrl]

No neither of them did. Do you mean a mismatch between the router/firewall and the passport?

 

[AyrishGrl]

Our router and firewall are set with MTU of 1500. Where can I check the MTU on the passport?

 

[AyrishGrl]

I think I just found the MTU setting.

Chassis Info :

Chassis : 8010
Serial# : SSNM0028WF
HwRev : A
NumSlots : 10
NumPorts : 162
GlobalFilter: enable
VlanBySrcMac: disable
Ecn-Compatib: enable
BaseMacAddr : 00:04:dc:d6:e0:00
MacAddrCapacity : 1024
Temperature : 28 C
MgmtMacAddr : 00:04:dc:d6:e3:f4

System MTU : 1950
clock_sync_time : 60

Should I try setting the MTU to match the Ciscos? Or the other way around? Would this mismatch cause discards and intermittant latency?

 

[netmanrick]

This is from menory.I think you have to add 20 bytes to the Cisco mtu for optimal data flow. I would call Nortel again just to be sure,I will search for the info.

Rick Harris
SC Dept of Motor Vehicles
Network Operations

 

[AyrishGrl]

We are going to change the Passport MTU to 1522 this weekend. Everything else in our network is set to 1500 so this makes more sense to me. All our other Nortel equipment is at 1500 so I am not sure why the Passport defaults to 1950. Nortel doesn't seem to want me to change the MTU yet they can't give me a good reason not to either. What are your thoughts on this? Thanks again for the help.

 

[netmanrick]

I checked both our 8600's.MTU is default to 1950. Of course we have no CISCO equipment in the equation.
I can't locate the info I referenced in a previous post about mtu mismatch.
Someone at Nortel or Cisco should know about this.
Sorry I can't do more.
Hopefully JIMBOPALMER will read this post;he goes way back on Nortel.

Rick Harris
SC Dept of Motor Vehicles
Network Operations