3845 Best Route Between Two Links

[dtom]

We have a 3845 router at one of our remote sites.  We want to connect the router to our central office using the two gigabit ports.  One link would be the primary and the other would be the secondary (backup).  The router is running EIGRP and the two ports would have diffrent ip addresses. How can we set up the router to use gi0/0 as the primary port and gi0/1 as the secondary (backup) port?  The backup port would only be used if there was congestion on the primary port or if the primary port went down.  Is there a way to force the router to make the primary link the best route?

Remote Router Sample Config:

!

int gi0/0

  desc primary link to Central Office

  ip addr 10.0.1.84 255.255.255.0

  duplex auto

  speed auto

!

int gi0/1

  desc backup link to Central Office

  ip addr 10.0.2.84 255.255.255.0

  duplex auto

  speed auto

!

router eigrp 64

  network 10.0.0.0

  network 172.16.0.0

  no auto-summary

!

Central Office Sample Config

!

int gi0/0

desc primary link to Remote Offices

ip addr 10.0.1.254 255.255.255.0

duplex auto

speed auto

!

int gi0/1

desc backup link to Remote Offices

ip addr 10.0.2.254 255.255.255.0

duplex auto

speed auto

!

router eigrp 64

network 10.0.0.0

network 172.18.0.0

no auto-summary

!

[Jose Bogantes]

Hello Dtom,

Please check the following link:

Q.    How can I use only one path when a router has two equal cost   paths?

A. Configure the bandwidth value on the interfaces to default, and       increase the delay on the backup interface so that the router does not see two       equal cost paths.

http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a008012dac4.shtml

Try something like this and let me know if it works:

R4(config)# interface GigabitEthernet0/1R4(config-if)# delay 10

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c2d96.shtml#delayparaR4

(The default delay is 1 when configured under the interface and it equals 10 microseconds )

3845_2(config-if)#delay ?

  <1-16777215>  Throughput delay (tens of microseconds)

If you use "delay 10", the interface will look this:

3845_2(config-if)#do sho int giga0/1

GigabitEthernet0/0 is up, line protocol is down

  Hardware is BCM1125 Internal MAC, address is 0015.629a.8aa0 (bia 0015.629a.8aa0)

  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 100 usec,

     reliability 255/255, txload 1/255, rxload 1/255

Regards.

[kecorder]

Remember to change The delay on The router receiving the update, not the one sending it. On the other hand the route will not change if interface is congested, only PfR can do that...

Sent from Cisco Technical Support iPhone App

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

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In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

Remember to change The delay on The router receiving the update, not the one sending it.

Eh?

Believe if you have two equal cost paths, from two ports, on the same router, you'll want to adjust the EIGRP delay on at least one of those ports.

[kecorder]

Yes if you recieve two routes you can change the delay on one of the interfaces, I just wanted to remind you you need to change the delay on the interface that recieves the route, not on The router that sends The route

Sent from Cisco Technical Support iPhone App

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Ah, I understand what you're saying now.

Thanks.

[Rahul Kukreja]

One Other option -

Use Summarization. Advertise summary routes over backup link and specific over the primary Link