ip hop in traceroute

[suthomas1]

a strange problem occurs with one of our remote subsidary locations.our users try to acces

10.123.2.100 at destination site via mpls. the site can be seen by users and do their functions.

problem is with trace output below. 5,6,7,8 are last 4 trace outputs.

wan router ----> layer 2 application device ------> layer 3 device

5   215 ms   211 ms   217 ms  202.82.174.27  

6   217 ms   217 ms   217 ms  202.82.174.28   >>> WAN router at remote site

7   218 ms   217 ms   218 ms  10.123.2.110   

8   218 ms   218 ms   218 ms  xyz.server.com 10.123.2.100  >>>>>> actual destination server

10.123.2.110 & 10.123.2.100 both are attached to a another layer3 device after the wan router.

and are configured for NAT on this layer 3.

wan router 202.82.174.28 shows both these 10.123.2.110/100 as directly connected segment.

lan interface of wan router is 10.123.2.102.

How hop 7 comes if actual destination is hop 8, shouldnt destination

10.123.2.100 be showing on hop 7 instead.

I am also told that in between router & layer 3 device there is a application related device ,although it

does only layer 2 function.

All help will be appreciated.

TIA

[Mahesh Gohil]

Hello,

Is it possible to provide

> Trace from wan router to 10.123.2.100

> Trace from wan router to user ip (source)

> config for layer-3 device/wan router

Regards

Mahesh

[suthomas1]

this is trace from router.

Type escape sequence to abort.

Tracing the route to 10.123.2.100

  1 10.123.2.110 0 msec 0 msec 0 msec

  2 10.123.2.100 4 msec 0 msec 4 msec

i do not hold privilege to get configuration of wan router.also , i will have to ask support personnel for the actual sources.

[milan.kulik]

Hi,

ain't that possible the  10.123.2.110 device is providing a NAT for some device behind it NATing the real address to 10.123.2.100?

Are you able to get sh arp from the WAN router and check if the MAC addresses assigned to  10.123.2.110 and 10.123.2.100 aren't the same?

HTH,

Milan

[suthomas1]

Thanks Milan.

Yes, the arp says both are same, with difference in their ages.

10.123.2.110             4   0031.c487.e145  ARPA   FastEthernet0/1

10.123.2.100        219    0031.c487.e145  ARPA   FastEthernet0/1

as per your post, 10.123.2.110 device is providing nat to a device behind it. will that be possible if 10.123.2.110 is only a nat used ip and not used on any interface on the L3 device.

Appreciate your help on this.

TIA.