From: Vikram Dadlaney (vdadlaney@gmail.com)
Date: Tue Sep 05 2006 - 14:34:19 ART
Hi Nikhar,
I believe this might have something to do with the fact that locally
originated traffic is always processed switched. HTH.
On 9/5/06, nikhar Wilder <nikhar.n@gmail.com> wrote:
>
> 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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