Solved: scenario for WS-C4900M

kozorezdi · ‎03-23-2010

Good day everybody,

i have a question about WS-C4900M.

it can has up to 24 10Gb (fiber) ports. I understand the main purpose of this device as a L2/L3 switch, but...

it looks like i can create bgp sessions directly on this device. for example, i can create a connection to my upstream and a few main bgp customers on this switch. as result, main traffic will be delivered without transporting over whole my network. i see, it has only 512mb RAM... but maybe somebody uses it in such manner or was trying to do it

what do you think about such scenario?

--

Thank you in advance,

Dmitry

Giuseppe Larosa · ‎03-23-2010

Hello Dmitry,

being a multilayer switch there are no problems in the forwarding plane.

However, in the signalling plane there will be limits in how many routes can be handled by the processor and how many IP prefixes can be stored in the CEF tables.

The datasheet does not provide figures for these parameters

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6021/ps9310/Data_Sheet_Cat_4900M.html

You cannot expect to handle full internet tables on this device it is not designed for this.

Efficient forwarding happens if all IP prefixes can be stored in the CEF TCAM tables otherwise cpu will hit 100% and the system can become not usable.

Just for comparison, on a C6500 you need at least sup720 3BXL to handle full internet table and DFCs must be DFC 3BXL or DFC 3CXL in order to work correctly.

A lower supervisor but even a single lower DFC can cause serious problems

Hope to help

Giuseppe

View solution in original post

Giuseppe Larosa · ‎03-23-2010