Re: [nv-l] Trap source

["Alan E. Hennis" <Hennis_Alan_E@cat.com>]

Bill

The trap will be recorded as it is received.

When a Cisco router sends a packet sourced from the router it will use the
egress interface as the source IP address of the packet. So when you Cisco
router sends a trap it will use as a source address the interface of that
the packet leaves the router. So if the packet goes out

10.18.109.46 () Serial1/0.1

the source address will be 10.18.109.46. If it goes out one of the other
interfaces it will use the IP address of that interface.

On my routers that have Loopback interface I use the following command.

      snmp-server trap-source loopback 0

to force the router to use the loopback as the source address.

Thanks
Alan E. Hennis
Caterpillar Inc.
Systems+Process Division
309.494.3308
hennis_alan_e@cat.com


                                                                                
                                                       
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                      08/10/2004 03:03                                          
                                                       
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                      Please respond to   Subject:      [nv-l] Trap source      
                                                       
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Caterpillar: Confidential Green                 Retain Until: 09/09/2004
                                                Retention Category:  G90 -
                                                General
                                                Matters/Administration




Hi,

I'm running NV 7.1.4 on AIX 5.2

I thought I understood something about how a trap source was logged in
trapd.log but I've seen something that challenges my understanding. I have
a router with a loopback interface and 5 frame relay interfaces like so.
Name resolution is shown in parenthesis:

router1.domain.net (192.168.14.1) Cisco Router
             192.168.14.1 (router1.domain.net) Loopback0 -- Software
Loopback
             10.11.1.254 () Serial0/0.1 -- Frame Relay
             10.11.3.254 () Serial0/1.1 -- Frame Relay
             10.12.100.254 () Serial0/0.2 -- Frame Relay
             10.12.102.254 () Serial0/1.2 -- Frame Relay
             10.18.109.46 () Serial1/0.1 -- Frame Relay

I seem to recall determining empirically that even if a trap was sent by
this router with the source as one of the serial interfaces, the trap would
be logged with a source of router1.domain.net. Recently I have been seeing
traps from this device with a source of 10.18.109.46. Is my understanding
as described here wrong? Will the trap source always be recorded just as it
was received?

Thanks,
Bill Kellam
Enterprise Integration and Management