From: nikhar Wilder (nikhar.n@gmail.com)
Date: Tue Sep 05 2006 - 13:26:22 ART
Thanks Vincent. I think that's the case. Something mind boggling is, that
Trace always sends 3 packets with varying TTL's regardless of the hop/node
it's ran from but yet i only see this kinda output from the router closest
to the destination but not from anywhere else. Maybe there's more to it or
there's something i'm missing.
On 8/29/06, Vincent Mashburn <vmashburn@fedex.com> wrote:
>
> Looks like you are using EIGRP with equal cost routes. Since traceroute
> sends 3 packets at a time, I believe that what you are seeing is the
> result of equal cost load-balancing.
> Thanks
> Vince Mashburn
> Voice / Data Engineer
> 901-263-5072
> CCVP, CCNP, CCDA,Network +
> Cisco IP Telephony Support Specialist
> Cisco IP Telephony Operations Specialist
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> nikhar.n@gmail.com
> Sent: Tuesday, August 29, 2006 1:53 AM
> To: ccielab@groupstudy.com
> Subject: Weird Traceroute Behaviour...Need assistance
>
> Hello All,
>
> I'm currently preparing for the ccie lab exam as well as work as a
> Network engineer for a local Enterprise. A few days ago i've come across
> a traceroute behaviour that i can't fully decipher and need some
> assistance with. Below is the topology diagram for the remote site with
> a modified version of the ip addressing scheme.
>
> The site comprises of 2 3825 wan routers which are connected to directly
> over subnet .3 thru g0/1 interfaces as well over subnet .2. A point to
> note is that g0/0 on both routers connect to switchports running in
> access mode in vlan 2 on the 2 3750 series catalyst switches being used
> as core switches as it's a small office. Both switches also have their
> respective vlan 2 SVI's with the hosts ip's of 2.2 and 2.3. So
> essentially, vlan 2 comprises of 4 routable interfaces (2 g0/0
> interfaces on wan routers and 2 Routable SVI's on both the cores). Core
> 1 is the primary stp root and hsrp primary for the all user vlans. A
> user switch is dual homed to both the cores. The user switch consists of
> vlan 10 int with an ip 192.168.10.20. EIGRP is the IGP being used
> throughout the corporate and is enabled on all l3 interfaces.
>
> T1-Pri-circuit waiting for a backup circuit
> |
> | |
> |g0/1 192.168.3.0/30 g0/1 |
> Wan Router 1 ==================== WAN Router 2
> g0/0 g0/0
> 192.168.2.5 192.168.2.6
> | |
> | HSrp: .1 (Core 1 Active) |
> | |
> | |
> | |
> Vlan int 2 - Core1 Vlan int 2 - Core2
> 192.168.2.2 192.168.2.3
> 192.168.2.20(Sec) 192.168.2.19 (sec)
> | |
> | L2 , All vlans |
> Core 1 ============================= Core 2
> | Vlan10 |
> | 192.168.10.x/24 |
> | |
> | HSRP: .1 |
> | |
> | vlan 28 |
> |___________User switch______________|
>
>
> Issue:
>
> When i traceroute to the vlan int 10 on user switch from either of the
> wan routers. I get the following results.
>
> trace 192.168.10.20
>
> Type escape sequence to abort.
> Tracing the route to 10.190.10.20
>
> 1 192.168.2.3 0 msec (core 2)
> 192.168.2.2 0 msec (core 1)
> 192.168.2.3 4 msec (core 2)
> 2 192.168.10.20 0 msec * 0 msec
>
> Upon checking the route table, I can see the that there's two gateways
> available for the packets
>
> D 192.168.10.0/24 [90/3072] via 192.168.2.3, 7w0d,
> GigabitEthernet0/0
> [90/3072] via 192.168.2.2, 7w0d,
> GigabitEthernet0/0
>
> Upon checking the ip cef table, i can see that the packets will be sent
> to 192.168.2.3 as per following
>
> #sh ip cef exact-route 192.168.2.4 192.168.10.20
> 192.168.2.4 -> 192.168.10.20 : GigabitEthernet0/0 (next hop
> 192.168.2.3)
>
> Question is, what does this trace route represent. I dont think it's a
> routing loop since vlan 10 is a directly connected interface on both
> cores and the packets should be switched locally. The part that really
> puzzles me is the 2nd line of the trace route which seemingly suggests
> packet bouncing between the cores before finally making its way back to
> core 2(third line of trace route) and then getting delivered via the
> directly connected interface of vlan 10.
>
> Any feedback will be greatly appreciated on this.
>
> TIA
>
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