4900M layer 3 switch routing limitations.

[davidvanrensburg]

Hi All,

Im strugging to find information pertaining to the number of routes allowed on this router / switch.

We use a 4900M as a peering router due to it only being 2u and having plenty port density and not being that expensive.

There are articles online from cisco that mention a 250k route limit as well as a 300k route limit. Is this a TCAM limitation or a software license issue ?

We are running enterprise services but I dont think that matters. 

How do we see on the IOS what the limit is and how far its exausted ?

How do I know if thats a bgp table limitation or a ip route limitation ? ie sh ip route or sh ip bgp

As far as I know this is not a normal memory issue ? How do we see TCAM size as far as I understand routes are all in TCAM.

[Georg Pauwen · Accepted solution]

Hello,

the 4900M has 512Mb default RAM (fixed) which would approximately coincide with 300K routes. The limiting factor is RAM, and obviously what the CPU can handle.

The IOS will only tell you indirectly whether you are reaching the limit, by looking at the memory and CPU utilization.

[davidvanrensburg]

Hi

It looks like it has 1 gig :

ter-cpt-01#show memory summary

                Head    Total(b)     Used(b)     Free(b)   Lowest(b)  Largest(b)

Processor   146A379C   999671904   328939688   670732216   669141772   670329688

I heard the limiting factor is TCAM and not RAM ?

How do i see the TCAM utilisation ? Is it sh ip route plus sh ip bgp ?

[Georg Pauwen]

Hello,

the 4948E and the 4948E-F have 1Gb of default SDRAM; either way, I think the command to view FIB TCAM utilization on the 4900 is:

show platform hardware ip route summary

[davidvanrensburg]

hi 

thanks very much

the output gives me a lot of information that i dont understand at all however this section seems relative please advise ?

entity        total     used      free      util%                              

Entries       258048    98240     159808    38                                 

  uRPF Ipv4   0         0         0         0                                  

  uRPF Ipv6   0         0         0         0                                  

  UC Ipv4     102400    98237     4163      95                                 

  MC Ipv4     2048      2         2046      0                                  

  UC Ipv6     2048      1         2047      0                                  

  MC Ipv6     0         0         0         0                                  

  SpecDst     0         0         0         0                                  

  SpecSrc     0         0         0         0                                  

  unused      151552    151552    0         100                                

does the total of 258k mean the total routes allowed ?

So the limit is the tcam and not ram correct ?

Is this a hardware limit or a limit cisco put into software to make one upgrade ?

[Georg Pauwen]

Hello,

can you post the output of 'show version' ? I am running the output of the command above through the CLI Analyzer...

[davidvanrensburg]

sure: 

ter-cpt-01#sh ver

Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500e-ENTSERVICESK9-M), Version 12.2(54)SG, RELEASE SOFTWARE (fc3)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2010 by Cisco Systems, Inc.

Compiled Sun 27-Jun-10 09:28 by prod_rel_team

Image text-base: 0x10000000, data-base: 0x12E09514

ROM: 12.2(44r)SG10

Sushi Revision 11, Tatooine Revision 141, Forerunner Revision 1.78

ter-cpt-01 uptime is 3 weeks, 4 days, 2 hours, 20 minutes

System returned to ROM by power-on

System restarted at 19:45:04 SATIME Thu Jan 5 2017

System image file is "bootflash:/cat4500e-entservicesk9-mz.122-54.SG.bin"

This product contains cryptographic features and is subject to United

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Importers, exporters, distributors and users are responsible for

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agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to

export@cisco.com.

cisco WS-C4900M (MPC8548) processor (revision 5) with 1048576K bytes of memory.

Processor board ID JAE17370DJ1

MPC8548 CPU at 1.33GHz, Cisco Catalyst 4900M

Last reset from PowerUp

12 Virtual Ethernet interfaces

32 Gigabit Ethernet interfaces

24 Ten Gigabit Ethernet interfaces

511K bytes of non-volatile configuration memory.

Configuration register is 0x2102

ter-cpt-01#

[Georg Pauwen · Accepted solution]

Hello,

my bad. Apparently the output of that command 'show platform hardware ip route summary' is only available to TAC...

[davidvanrensburg]

Hi Georg

THank you your command does work.

Does using soft-reconfigutation use extra tcam memory or normal memory ? 
We are running out of tcam is there something we can do ?

[Joseph W. Doherty]

BGP's soft-reconfig should use RAM.  Later BGP implementations shouldn't need to use it.

About the only thing you can do to reduce TCAM usage is to reduce your demand on it.  For example, filter your BGP intake to reduce your number of prefixes.