ping command to look every time for the next hop

['chris']

hi

how is the ping command to look every time for the next hop ?

for example:

first ping:

# ping 192.168.24.1 -c 4

PING 192.168.24.1 (192.168.24.1) 56(84) bytes of data.
From 192.168.0.10: icmp_seq=1 Redirect Host(New nexthop: 192.168.0.15)
64 bytes from 192.168.24.1: icmp_seq=1 ttl=255 time=37.8 ms
64 bytes from 192.168.24.1: icmp_seq=2 ttl=255 time=33.6 ms
64 bytes from 192.168.24.1: icmp_seq=3 ttl=255 time=35.1 ms
64 bytes from 192.168.24.1: icmp_seq=4 ttl=255 time=37.8 ms

--- 192.168.24.1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3002ms
rtt min/avg/max/mdev = 33.658/324.144/37.895/1.831 ms


second ping:

# ping 192.168.24.1 -c 4

PING 192.168.24.1 (192.168.24.1) 56(84) bytes of data.
64 bytes from 192.168.24.1: icmp_seq=1 ttl=255 time=34.7 ms
64 bytes from 192.168.24.1: icmp_seq=2 ttl=255 time=36.2 ms
64 bytes from 192.168.24.1: icmp_seq=3 ttl=255 time=37.1 ms
64 bytes from 192.168.24.1: icmp_seq=4 ttl=255 time=34.3 ms

--- 192.168.24.1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3003ms
rtt min/avg/max/mdev = 34.393/35.641/37.153/1.152 ms

first ping looks for the next hop but following next one it doesn't.

kind regards
chris

[Vitaly Karasik_1]

as far as I understand, first time when you try to reach remote host, you machine receives a routing information from its default router. Next time your machine already has it in its cache.

[Steven E. Protter]

Shalom,

netstat -rn
# before the command
netstat -rn
# after the first ping.

You should see the routing tables updated.

ifconfig eth#

Your routing/network environment is the source of this issue.

SEP

['chris']

thanks,

but howto delete the routing cache ?

[Vitaly Karasik_1 · Accepted solution]

"ip route flush cache" should delete all entries.

BTW, do you have some network problem or you just curious how it works?

[Sergejs Svitnevs]

You need only add new route:
# route add -net 192.168.24.0 netmask 255.255.255.0 gw 192.168.0.15

Regards,
Sergejs

['chris']

thanks, but this command doesn't work on my Debian Sarge Stable:

linux:~# ip route flush cache
-bash: ip: command not found

I've written a small perl program to check the routing and I must delete the routing cache all the time before I do a ping


and:

# route add -net 192.168.24.0 netmask 255.255.255.0 gw 192.168.0.15

will not help in my case.

greetings
chris

['chris']

thanks a lot

# apt-get install iproute

helps

and

# ip route flush cache

solved my problem !