emulation with GNS3

[Abdelilah Benrida]

Hi

i'm usig GNS3 and i have to deal with this situation:

R5 has NM-1FE-TX modul (connected to R4).

R5 has also NM-16ESW modul (connected to R1,R2 and R3).

here are the config :

R4 :

!

interface FastEthernet0/0

ip address 190.1.1.1 255.255.255.0

duplex auto

speed auto

!

interface FastEthernet2/0

ip address 190.1.2.1 255.255.255.0

duplex auto

speed auto

!

no ip http server

no ip http secure-server

!

ip classless

ip route 191.1.1.0 255.255.255.0 190.1.1.2

ip route 191.1.1.0 255.255.255.0 190.1.2.2

!

!

R5:

ip dhcp excluded-address 191.1.1.1 191.1.1.10

!

ip dhcp pool URNE

   network 191.1.1.0 255.255.255.0

   default-router 191.1.1.1

!

!

interface FastEthernet0/0

ip address 190.1.1.2 255.255.255.0

duplex auto

speed auto

!

!

interface FastEthernet2/0

ip address 190.1.2.2 255.255.255.0

duplex auto

speed auto

!

!

interface FastEthernet1/11

switchport access vlan 10

!

interface FastEthernet1/12

switchport access vlan 10

!

interface FastEthernet1/13

switchport access vlan 10

!

!

interface Vlan10

ip address 191.1.1.1 255.255.255.0

!

R1 :

!

interface FastEthernet0/0

ip address dhcp

duplex auto

speed auto

!

R2 :

!

interface FastEthernet0/0

ip address dhcp

duplex auto

speed auto

!

R3 :

!

interface FastEthernet0/0

ip address dhcp

duplex auto

speed auto

!

R1#ping 190.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/30/52 ms

R1#ping 190.1.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/42/68 ms

R2#ping 190.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 20/39/68 ms

R2#ping 190.1.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 20/39/60 ms

R3#ping 190.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 20/38/72 ms

R3#ping 190.1.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/32/72 ms

EVREY THING IS FINE :

now i will shutdown interface f0/0 of R5:

R5(config)#interface f0/0

R5(config-if)#sh

R5(config-if)#end

R5#

*Mar  1 00:24:58.887: %SYS-5-CONFIG_I: Configured from console by console

*Mar  1 00:24:59.799: %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to administratively down

R5#

*Mar  1 00:25:00.799: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to down

And i ping from routers R1, R2 and R3 190.1.2.1 (other link :(f2/0-----f2/0)).

R1#ping 190.1.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 20/32/64 ms

R2#ping 190.1.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.2.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

why R2 can't ping and R1 can ?

R3#ping 190.1.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 190.1.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 24/53/84 ms

[cadet alain]

Hi,

on R4 f0/0 is still UP( that's GNS3 behaviour) and so both routes stay in the routing table of R4 and if R4 decided to forward the traffic out this interface then it is failing. You should implement tracking with IP SLA on your first  static route on R4 and it will delete the route from the routing table when R5 next-hop is unreachable and it will only have one route and so one interface to send the replies and it will work.

Regards

Alain

Don't forget to rate helpful posts.

[Abdelilah Benrida]

is this correct ?

ip sla monitor 1

type echo protocol ipIcmpEcho 190.1.1.2 source-interface FastEthernet0/0

frequency 5

ip sla monitor schedule 1 life forever start-time now

!

!

!

track 1 rtr 1 reachability

!

ip route 191.1.1.0 255.255.255.0 190.1.1.2 track 1

ip route191.1.1.0 255.255.255.0 190.1.2.2 254

[cadet alain · Accepted solution]

Hi,

this is correct but to really get sure your IP SLA probes go out f0/0 you  should do this:

access-list 199 permit icmp any host 190.1.1.2

route-map SLA

match ip add 199

ip local policy route-map SLA

Regards

Alain

Don't forget to rate helpful posts.

[Abdelilah Benrida]

thank you  very much ,you saved me