7204 vxr fa mtu

Do you own all of the equipment end -to-end ?

What are the Cisco switch model numbers ?

Oh and what else do the 7204's connect to ?

yes I do own it and I am not sure about switches exactly, routers are connected to 4506 and those fiberoverip switches are connected to 4506 also. Point is that fiberoverip link is not working and storage people are telling me that mtu MUST be 2500. But we did some tests with both storage systems on one location, connected over 10M half duplex eth and default

1500 mtu and everything worked ok.

Do the data flows have to go thru your router or can they just flow over you 4506 switches ?

What supervisor do you have on the 4506 - SUP V ?

If you have a SUP V, are you using the GE ports ?

Do you know the make and model of the SAN storage devices ?

Do you know the performance and throughput requirements for the storage devices ?

they have to go through switches. SAN switches are MDS 9216. On 4506 sup mod is II+ and SAN switch is connected to ports that support jumbo frames (2 GBIC on sup mod). SAN devices are some kind of EMC disks. I do not know throughput requirements but in this stage I need to solve jumbo frames on complete path between SANs, wich means MDS - 4506 - 7204 - ATM network -

7204 - 4506 - MDS. So far I am stuck with 7204 eth ports.

Your last post really clarified your setup - thanks.

Is the only role that the 7204 plays is to connect 4506 to ATM WAN ?

Or are there other devices connected to 4506?

other devices also. Both locations I am talking about has cca 200 people working on it. ATM link is 6Mb between locations. There is QOS on link and I can ping between MDS switches

7204 options for Gigabit Ethernet connection to 4506 switch

MTU can be as high as 4470

a) NPE-GE1

b) PA-GE

I know but I do not have those interfaces. So I have two options

1. eithere buy them
2. or convince SAN guys that MTU higher then 2500 is not MANDATORY

I've read som doc about this and I think that MTU highrt then 2500 is not mandatory. What do you think?

A bigger MTU will probably provide higher throughput between the SAN devices.

What is essential is not to end up fragmenting packets.

For starter take a look at the following Cisco doc:

this is my opinio also. But because link between locations is ATM, we cannot avoid fragmentation. Am I right? And on one side it is E3 connection to ATM network and on other location it is 8xE1 IMA group, yet another source of fragmentation and mybe "out-of-order" packets. But mybe because fragmentation is on layer 2, mybe TCP packet i reasamled ok? What do you think?

Thanks!

When I was speaking of fragmentation it was at layer 3 (i.e. IP fragmentation).

Clearly with ATM there is L2 fragmentation.

I would suggest that you baseline the busy-hour ATM link utilization and latency before the SAN load is imposed.

Lower MTU(i.e. 1500) will work but throughput for SAN will not be as good.

You should also consider whether you want the SAN traffic going thru your 4506 switches or whether it should go directly into the 7204 using a PA-FC-1G. Also you will need to determin if the 7204 will need a processor upgrade.

Are your running VOIP over the ATM link ?

:-)) yes we are running voip. I guess we can replace MDS switches on both side wirh PA-FC-1G modules?

1. Do you have low latency queueing(LLQ) configured for VOIP

1. Do you have a Cisco SE or do you acquire your gear thru a distributor?

2. Do you have a detailed VISIO diagram for the current setup ( I can provided private email id)

OBTW what are the availability requirements for the SAN to SAN connection over your WAN ?

1. yes
2. distributor
3. will see tommorow

offline sinc, over night, not real time