×

Warning message

  • Cisco Support Forums is in Read Only mode while the site is being migrated.
  • Cisco Support Forums is in Read Only mode while the site is being migrated.

failover on two different links

Answered Question
Nov 28th, 2006
User Badges:

how can i apply the failover concept, if i have customer connected to a 3750 switch and two uplinks that are pointing to two different networks. the customer gateway points to the first uplink, how can the other uplink send the customer's traffic to the internet if the first uplink failed?

Correct Answer by amit-singh about 10 years 8 months ago

If you have 3 of these 3750's. You can have a hub and spoke topology. Like this


Use 3750 A for client connectivity

Use 3750 B for say ISP 1 with one of the host connected to it.

use 3750 C for ISP 2 and have a trunk between 3750B and 3750C with the SVI's configured.


So 3750 A is connected to 3750B and 3750C on routed port.


On 3750 a Put you client on vlan1 and create a SVI for it. Put the ports connected to 3750B and 3750 C on a routed port


On 3750A

Conf t


ip routing


int vlan 1

ip address 1.1.1.1 255.255.255.0

no shut


int fa 0/1

no switchport

ip address 2.2.2.1 255.255.255.0

no sh


int fa 0/2

no switchport

ip address 3.3.3.1 255.255.255.0


ip route 0.0.0.0 0.0.0.0 2.2.2.2

ip route 0.0.0.0 0.0.0.0 3.3.3.2 200


On 3750 B :->


Conf t

ip routing

int vlan 2c--> Connect your PC on Vlan2

ip address 11.11.11.1 255.255.255.0

no shut


int fa 0/1

no switchport

ip address 2.2.2.2 255.255.255.0

no sh


int fa 0/2 -> trunk to 3750C

switchport encapsulation do1tq

switchport mode trunk


ip route 1.1.1.0 255.255.255.0 2.2.2.1

ip route 1.1.1.0 255.255.255.0 11.11.11.2


On 3750 C :->


Conf t

ip routing

int vlan 2

ip address 11.11.11.2 255.255.255.0

no shut


int fa 0/1

no switchport

ip address 3.3.3.2 255.255.255.0

no sh


int fa 0/2 -> trunk to 3750B

switchport encapsulation do1tq

switchport mode trunk


ip route 1.1.1.0 255.255.255.0 3.3.3.1

ip route 1.1.1.0 255.255.255.0 11.11.11.1


Once that is done and you are pinging from the host on 3750 A to host on 3750B, go ahead and disconnect the cable between 3750A and 3750B, the traffic should pass through 3750C.


HTH,

-amit singh



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4.5 (2 ratings)
Loading.
ankbhasi Tue, 11/28/2006 - 00:24
User Badges:
  • Cisco Employee,

Hi Sawsan,


When you say 2 different networks you mean 2 different subnets? The 2 Uplinks are connected to different subnets on 2 different routers?


Ankur

sawsan.mohamed Tue, 11/28/2006 - 00:41
User Badges:

Hi ankbhasi,


yes, for example, the first uplink (213.42.87.0), the second uplink (80.17.60.0)on two different routers



ankbhasi Tue, 11/28/2006 - 00:56
User Badges:
  • Cisco Employee,

Hi Sawsan,


Instaead of defining a gateway can we have 2 static routes pointing to 2 different address with second one having higher admin distance.


Something like this


ip route 0.0.0.0 0.0.0.0 200

ip route 0.0.0.0 0.0.0.0 220


In this case when first link goes down the second static route will take the action.


Regards,


Ankur

sawsan.mohamed Tue, 11/28/2006 - 01:34
User Badges:

how can I test this concept and prove it, if i'm having 3 of Cisco 3750?

ankbhasi Tue, 11/28/2006 - 01:51
User Badges:
  • Cisco Employee,

Hi Swasan,


If this 3750 working as a complete layer 2 switch? or you are using it as a layer 3 edge for customer?


Ankur

Correct Answer
amit-singh Tue, 11/28/2006 - 01:53
User Badges:
  • Blue, 1500 points or more

If you have 3 of these 3750's. You can have a hub and spoke topology. Like this


Use 3750 A for client connectivity

Use 3750 B for say ISP 1 with one of the host connected to it.

use 3750 C for ISP 2 and have a trunk between 3750B and 3750C with the SVI's configured.


So 3750 A is connected to 3750B and 3750C on routed port.


On 3750 a Put you client on vlan1 and create a SVI for it. Put the ports connected to 3750B and 3750 C on a routed port


On 3750A

Conf t


ip routing


int vlan 1

ip address 1.1.1.1 255.255.255.0

no shut


int fa 0/1

no switchport

ip address 2.2.2.1 255.255.255.0

no sh


int fa 0/2

no switchport

ip address 3.3.3.1 255.255.255.0


ip route 0.0.0.0 0.0.0.0 2.2.2.2

ip route 0.0.0.0 0.0.0.0 3.3.3.2 200


On 3750 B :->


Conf t

ip routing

int vlan 2c--> Connect your PC on Vlan2

ip address 11.11.11.1 255.255.255.0

no shut


int fa 0/1

no switchport

ip address 2.2.2.2 255.255.255.0

no sh


int fa 0/2 -> trunk to 3750C

switchport encapsulation do1tq

switchport mode trunk


ip route 1.1.1.0 255.255.255.0 2.2.2.1

ip route 1.1.1.0 255.255.255.0 11.11.11.2


On 3750 C :->


Conf t

ip routing

int vlan 2

ip address 11.11.11.2 255.255.255.0

no shut


int fa 0/1

no switchport

ip address 3.3.3.2 255.255.255.0

no sh


int fa 0/2 -> trunk to 3750B

switchport encapsulation do1tq

switchport mode trunk


ip route 1.1.1.0 255.255.255.0 3.3.3.1

ip route 1.1.1.0 255.255.255.0 11.11.11.1


Once that is done and you are pinging from the host on 3750 A to host on 3750B, go ahead and disconnect the cable between 3750A and 3750B, the traffic should pass through 3750C.


HTH,

-amit singh



sawsan.mohamed Tue, 11/28/2006 - 03:22
User Badges:

thanks for both of you,


and thanks amit for the configuration..i will try to configure it and see the results.

bond12345 Tue, 11/28/2006 - 03:28
User Badges:

Hi,

If you have two links connecting on the same router,then the solution to send the traffic to other link when one fails is to put a static route with some higher metric.e.g

ip route 0.0.0.0 0.0.0.0 x.x.x.x 200

where x.x.x.x is the next hop ip address.

Actions

This Discussion