cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
854
Views
5
Helpful
2
Replies

traceroute and GRE

duleepchandimal
Level 1
Level 1

how traceroute display hops when there is a GRE tunnel in the middle of the path. for Example hop 1,2,3,4-------8 GRE,9,10,11,12,13,14,15. 

2 Replies 2

Reza Sharifi
Hall of Fame
Hall of Fame

The GRE tunnel is one hop no matter how many devices it goes over.

HTH

Reza

Hi,

if we create GRE tunnel for hop1 to hop5 and then normal IP path ,traceroute first display 8 th hop IP address as 5th hop.

PC------------>1-------------------------GRE--------------------5,6,7,8,9,10

if we traceroute from PC,

1. * * * (say node 1 node allowed to display its IP)

2. * * *

3. * * *

4. * * *

5. IP address of 8 th hop

6. IP address of 8 th hop

7. IP address of 8 th hop

this mean TTL reduce process starts at the end of GRE tunnel and it will go to TTL=0 at 8th hop. so it will not display hop 5,6,7 IP addresses. can this happen or IP payload TTL value should reduce according to number of hops passed through GRE at GRE end point.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Review Cisco Networking products for a $25 gift card