[cisco-bba] Re: L2TP sessions on 7200

[Anastassios Chatzithomaoglou]

I finally found what was the reason of process switched traffic and the high cpu load.

One of ours vpdn customers uses its own radius server in order to pass aaa attributes to 
its dialup clients. But it also passes "ip tcp header compression" to all its clients, so 
we had 500+ vaccess interfaces with tcp header compression enabled!!!

After disabling it, the cpu went down to 15%!!!

I couldn't imagine that tcp header compression could make such a difference (CPU x 3).

Thx to Dennis & Vincent for helping me out ;-)

Anastassios Chatzithomaoglou wrote:

> I have read a lot of conversations about 7200 and the max number of l2tp 
> sessions it can support, but all the answers are making me think that 
> there is something wrong with my case. My router doesn't even seem 
> capable of reaching 1000 sessions.
> 
> I have a 7206 (NPE-300) and with 550 sessions it reaches 50% - 60% cpu 
> load.
> Is there anything i can do in order to decrease it?
> "ip cef" doesn't seem to do anything...
> 
> 
> 
> IOS (tm) 7200 Software (C7200-IS-M), Version 12.2(15)T5,  RELEASE 
> SOFTWARE (fc1)
> ....
> cisco 7206VXR (NPE300) processor (revision D) with 229376K/65536K bytes 
> of memory.
> Processor board ID 21275620
> R7000 CPU at 262Mhz, Implementation 39, Rev 2.1, 256KB L2, 2048KB L3 Cache
> 6 slot VXR midplane, Version 2.1
> ....
> 
> router#sh proc cpu
> CPU utilization for five seconds: 51%/14%; one minute: 56%; five 
> minutes: 56%
> ...
>   45     3673508  23757648        154 13.81% 14.27% 14.10%   0 IP Input
> ...
>  119     5703560  21918620        260 17.22% 20.33% 20.45%   0 L2X Data 
> Daemon
> ...
>  143      610208     28956      21073  1.79%  1.76%  1.76%   0 VTEMPLATE 
> Backgr
> ...
> 
> This is what worries me most:
> 
> router#sh interfaces stat
> FastEthernet0/0
>           Switching path    Pkts In   Chars In   Pkts Out  Chars Out
>                Processor     180987   70971343     189373   75804748
>              Route cache      70067   34190251      88442   35201066
>                    Total     251054  105161594     277815  111005814
> 

-- 
***********************************
    Chatzithomaoglou Anastasios
Network Design & Operations Center
           FORTHnet S.A.
       <achatz at forthnet.gr>
***********************************