[c-nsp] 3750 Metro

[Cisco List]

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We've now got one deployed in production after some testing and will
likely deploy more.  We were off to a rocky start at first due to
some odd IOS issues.  Our main problem was MTU related, which
shouldn't be much of a surprise for anyone doing MPLS over ethernet
links on Cisco gear.  The box has a system MTU and a system jumbo
MTU.  With the current 12.2.x code the system MTU controls all MTU
settings for the entire box except for the MTU on the ES GigE ports. 
In theory that sounds ok but it isn't.  We found that the system MTU
command limits the mpls mtu command and there is no ip mtu command. 
So, what we ended up with was an MTU of 1546 on the ES GigE port's IP
interface (physical port was 9000) so OSPF was failing the MTU check.
 We were able to get around that but when we tried to map an EoMPLS
circuit it failed the MTU checks because it felt that port on the
3750 was 1546 and the remote side was 1500. There is no ip mtu
command in 12.2 currently.  From what the TAC said it was pulled from
12.2 because it didn't actually do anything.

We argued with the TAC some regarding how retarded this
implementation was.  In our opinion it made the box useless for one
of its primary functions (MPLS services) if you expect to run full
1500 byte frames.  We're used to setting 'ip mtu 1500' on interfaces
that have a higher MTU set for MPLS labels etc. and the boxes end up
happy.

We ended up getting the thing to work by reverting to some older code
12.1.X where the ip mtu command exists and the system and system
jumbo commands work as expected.  We now have the ES ports running at
9000 bytes, all IP interfaces at 1500 bytes, and MPLS interfaces at
1546.

In this configuration we were able to load up 12 ports of 10/100 and
two GigE ports and run them all at line rate using a SmartBits.  In
terms of performance we're happy with the box.  There is a new 12.2
release due out in the next week or so that apparently fixes the
crazy MTU commands.

All in all it seems to be a good box, just needs to mature some more.

Good luck,
Chad


- ----------------------------
Chad E Skidmore
One Eighty Networks, Inc.
http://www.go180.net
509-688-8180   

> -----Original Message-----
> From: Michel Renfer [mailto:michel.renfer at lan.ch] 
> Posted At: Tuesday, May 24, 2005 8:15 AM
> Posted To: Cisco List
> Conversation: 3750 Metro
> Subject: [c-nsp] 3750 Metro
> 
> 
> Hi All!
> 
> Anyone has informations regarding the (routing and mpls) 
> performance of the Catalyst 3750 Metro? Anyone using this 
> device in the field and is able to share his experiences?
> 
> cheers,
> michel
> 
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