[j-nsp] Juniper M20 memory problem

[Richard A Steenbergen]

On Mon, Jun 11, 2007 at 01:13:34AM +0200, Niels Bakker wrote:
> * nk at accelerated.de (Nicolaj Kamensek) [Sat 09 Jun 2007, 20:16 CEST]:
> >today I found the following messages in my /var/log/messages:
> >
> >Jun  9 19:59:53  re0 /kernel: Nexthop index allocation failed: regular 
> >index space exhausted
> >
> >nico at re0> show arp no-resolve | count
> >Count: 7205 lines
> 
> That's the maximum per FPC for the M20 platform.  It's not really suited 
> for functioning as an edge box.
> 
> (No, of course this isn't documented anywhere obvious)

For the entire box you mean, the M20 is a centralized platform so the 
limitation is on the SSB not the FPC. IIRC the way this was explained to 
me is that the limitation for L2 next-hops is actually due to the DRAM on 
the SSB and the default allocation of it rather than the SRAM.

To see the SRAM usage, which is normally what fills up as you put too many 
routes in (usually with routing-instances):

SSB0(router vty)# show jtree 0 memory    
Memory Statistics:
    8388608 bytes total (4 banks)
    3503816 bytes used
    4884792 bytes free
       8128 pages total
       3419 pages used
       4709 pages free
         31 max freelist size

I think the nh limitation can be seen by:

SSB0(router vty)# show nhdb zone    
Chip  Start   Size   Rsvd   Used/Hi Water/Total  Size  Name
----  -----  -----  -----  --------------------  ----  ----
   0  20000  01000  00000               0/0/512     8  Multicast RTP
   0  21000  02400  00000              0/0/9216     1  Multicast Lists
   0  23400  0d400  00006           16/22/54272     1  Next-Hop Entries
   0  30800  4f800  0004b        120/155/162816     2  L2 Descriptors
   0  40400  001ff  00000                5/6/63     8  L2 Programs
   3  20000  01000  00000               0/0/512     8  Multicast RTP
   3  21000  02400  00000              0/0/9216     1  Multicast Lists
   3  23400  04400  00006         722/769/17408     1  Next-Hop Entries
   3  27800  18800  0004b       2182/2323/50176     2  L2 Descriptors
   3  40400  001ff  00000                5/5/63     8  L2 Programs

Apparently the way some people have solved this is to upgrade the DRAM on 
the SSB (unsupported). The offical way to do it is to get an SSB-E-16 with 
larger SRAM and DRAM. But yeah an M20 just isn't a good platform for an 
edge box like this.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)