Author Topic: can ping but can not traceroute certain route  (Read 553 times)

ggnfs000 (OP)

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can ping but can not traceroute certain route
« on: May 04, 2017, 12:02:21 PM »
show ip route shows one R flagged address (rip v2 learned) which is valid route. The address was 100.100.100.4
I simply dont see this address anywhere in the network, period.

So I can presume that some reason it is stale route and ripv2 did not manage to remove through routing updates which itself weird but...

But I can ping it!
And can not traceroute it!

deanwebb

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Re: can ping but can not traceroute certain route
« Reply #1 on: May 04, 2017, 12:48:20 PM »
Do you have some device on your network that responds to pings for addresses that can't be routed?
Take a baseball bat and trash all the routers, shout out "IT'S A NETWORK PROBLEM NOW, SUCKERS!" and then peel out of the parking lot in your Ferrari.
"The world could perish if people only worked on things that were easy to handle." -- Vladimir Savchenko
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ggnfs000 (OP)

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Re: can ping but can not traceroute certain route
« Reply #2 on: May 04, 2017, 04:33:51 PM »
nope. this actually on packet trace software simulation with 4 routers and 2 switches.

wonder if it is a software bug.
will keep looking.
looks like a good troubleshooting exercise.

deanwebb

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Re: can ping but can not traceroute certain route
« Reply #3 on: May 04, 2017, 06:40:03 PM »
Well, then... the first question to you is, what are the differences between traceroute and ping?
Take a baseball bat and trash all the routers, shout out "IT'S A NETWORK PROBLEM NOW, SUCKERS!" and then peel out of the parking lot in your Ferrari.
"The world could perish if people only worked on things that were easy to handle." -- Vladimir Savchenko
Вопросы есть? Вопросов нет! | BCEB: Belkin Certified Expert Baffler | "Plan B is Plan A with an element of panic." -- John Clarke
Accounting is architecture, remember that!

ggnfs000 (OP)

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Re: can ping but can not traceroute certain route
« Reply #4 on: May 04, 2017, 09:04:21 PM »
Same except, well TTL starts from 0 for traceroute. What perplexes is how in the hell it is possible that ping can reach the non-existing target whereas traceroute can not. Trace route can ping next-hop but then after that goes blank.  :o

deanwebb

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Re: can ping but can not traceroute certain route
« Reply #5 on: May 04, 2017, 09:17:07 PM »
Keep thinking... how does a ping packet travel vs. how a traceroute packet? What is the difference in how they are handled by devices on the network?
Take a baseball bat and trash all the routers, shout out "IT'S A NETWORK PROBLEM NOW, SUCKERS!" and then peel out of the parking lot in your Ferrari.
"The world could perish if people only worked on things that were easy to handle." -- Vladimir Savchenko
Вопросы есть? Вопросов нет! | BCEB: Belkin Certified Expert Baffler | "Plan B is Plan A with an element of panic." -- John Clarke
Accounting is architecture, remember that!

ggnfs000 (OP)

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Re: can ping but can not traceroute certain route
« Reply #6 on: May 06, 2017, 12:46:38 PM »
so upon closer investigation, 100.100.100.4 was subnet showing up in "show ip route".
The actual interface in those subnets are 100.100.100.5 and 6 with mask 255.255.255.252 or /30.
still it does not describe why I ping 100.100.100.4.
Perhaps routing in IOS allows ping the subnet address somehow? Perhaps it is a "route to network"? Not only I can ping 100.100.100.4 also was able to ping subnet broadcast address 100.100.100.7.

As a comparison, I got home NAT subnet with 10.0.0.0 network, I can definitely NOT ping 10.0.0.0 let alone traceroute.
« Last Edit: May 06, 2017, 05:55:19 PM by ggnfs000 »

Dieselboy

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Re: can ping but can not traceroute certain route
« Reply #7 on: May 15, 2017, 10:48:54 AM »
You're thinking too broad, OP. Take a few steps back. I could be wrong, of course but - usually when I can ping but trace route is failing [somewhere] I go to [somewhere] and look at possibly why traceroute is not getting through [somewhere].

Hint: traceroute and ping are both icmp but they're different.

SimonV

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Re: can ping but can not traceroute certain route
« Reply #8 on: May 15, 2017, 10:54:32 AM »
Can you share the packet tracer file?

ggnfs000 (OP)

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Re: can ping but can not traceroute certain route
« Reply #9 on: May 18, 2017, 02:03:25 AM »
opened that packet tracer file before sending out but then now i can no longer ping 100.100.100.4!