Re: [Idr] BGP MIB v2 input

off-list,

On Mon, 26 Mar 2007, Bill Fenner wrote:
>> Just wondering: the current BGP4 MIB already supports the routing
>> databse (BGP4-MIB::bgp4PathAttrBest at least).  Are you proposing
>> dropping the equivalent functionality from the new MIB or just some
>> more exciting new variants?
>
> That was my proposal, since getting a pathattr table that
> nicely handles IP and non-IP NLRI is ... confusing.  It also
> can result in less than ideal behavior when walking the whole
> MIB on a device that has hundreds of thousands of prefixes.

If non-IP NLRI's are considerably difficult, maybe those should not be 
presented in the MIB (at least in the basic version)?

>> An example: I currently use both IP-FORWARD-MIB and
>> BGP4-MIB::bgp4PathAttrBest in SNMP scripts by parsing the config files
>> (interface-related routing protocol config to be exact) and checking
>> them against operational policy (e.g., certain kinds of interface
>> addresses must be in OSPF; others must not be in OSPF; some others
>> must be in BGP; static routes must be in BGP; etc.).
>
> Interesting.  I was looking it from the point of view of not knowing
> exactly what prefix you were looking for (e.g., "show ip bgp 12.106.35.1"
> without knowing that it's in a /22).  The obvious thing to do is to grab
> the whole table (probably inadvisable); there are more subtle ways but
> none are very efficient.

I'm not sure how the SNMP agent implementation actually does it (i.e. 
whether it needs to do memory copy of the whole table), but this what 
I do is without a subnet mask (because I have been too lazy to convert 
it between different prefix length representations :-):

$ snmpwalk -v 2c -c $comm -m BGP4-MIB $rtr bgp4PathAttrBest.193.167.190.0

BGP4-MIB::bgp4PathAttrBest.193.167.190.0.25.172.31.5.199 = INTEGER: true(2)
BGP4-MIB::bgp4PathAttrBest.193.167.190.0.30.172.31.5.199 = INTEGER: true(2)

.. and if I wanted to get more than just one prefix, I could walk a 
whole /16 with, e.g.:

$ snmpwalk -v 2c -c $comm -m BGP4-MIB $rtr bgp4PathAttrBest.193.166
...

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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