Alternate Static Route

md_ani · ‎05-02-2008

I have 3 locations viz. A, B & C. A is central location and is having E1 to B & C. For backup there is also a link between B&C. I have configure Static Route configured so that alternate path can be used if any link direct from location 'A' is down. What I have seen is as soon as the link goes down, traffic is not shifting to backup path automatically. Also what I have seen is althoug the link is down but it is showing UP when I am checking in Show Interface command. For this I manually need to shut the down link then only traffic is shifting to backup path. Sample config of a serial is mentioned below.

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description "Link A-B"

bandwidth 2048

ip address 192.168.2.50 255.255.255.252

no ip redirects

no ip unreachables

encapsulation ppp

no ip route-cache cef

no ip route-cache

no ip mroute-cache

no keepalive

no fair-queue

serial restart-delay 0

no dce-terminal-timing-enable

no cdp enable

***********************************

Pls help me so that traffic shifts to backup path automatically as soon as any link goes down.

Manish

guruprasadr · ‎05-02-2008

HI Manish [Pls Rate if HELPS]

The better recommendation on such cases is, migrate your Primary to some Dynamic Routing Protocol like RIP, EIGRP, OSPF. So when the routing protocol routes are withdrawn from the Routing table the next available static route with higher metric will be preferred.

The Viceveresa will also happen as easily as above.

In addition, the another feature of CISCO is, Birectional Forward Detection. Enabling BFD will help to withdraw the failed routes from the Routing table. Have attached the document for the Reference.

Configure as:

Router(config)#int fa0/1

Rotuer(config-if)#bfd interval 50 min_rx 50 multiplier 5

##Attachment in next POST##

Hope I am informative.

Pls Rate if HELPS

Best Regards,

Guru Prasad R

guruprasadr · ‎05-02-2008

HI Manish [Pls Rate if HELPS]

##Attachment available in this POST##

The better recommendation on such cases is, migrate your Primary to some Dynamic Routing Protocol like RIP, EIGRP or OSPF. So, when Primary Link fails the routing protocol routes are withdrawn from the Routing table & the next available static route with higher metric will be preferred.

The Viceveresa (ie., the fall back to Primary once it is Up) will also happen as easily as above. Since the Routing Protocol will be preferred over the static route with Higher Metric (eg: 200) once it becomes available.

In addition, the another feature of CISCO is, "Birectional Forward Detection". Enabling BFD will help to withdraw the failed routes from the Routing table. Have attached the document for the Reference.

Configure as:

==============

Router(config)#int fa0/1

Rotuer(config-if)#bfd interval 50 min_rx 50 multiplier 5

Hope I am informative.

Pls Rate if HELPS

Best Regards,

Guru Prasad R

md_ani · ‎05-02-2008

Thanks Guru Prasad R

Just confirm anything more need to be configured for EIGRP.

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router eigrp 100

redistribute connected

redistribute static

network 172.18.0.0

network 192.168.2.0

no auto-summary

no eigrp log-neighbor-changes

************************************

Manish

guruprasadr · ‎05-02-2008

HI, [Pls RATE if HELPS]

Your Configuration looks OK.

Note: Make sure to see if necessary to Configure the "EIGRP Timers" and "neighbor command". It depends on the requirement of your Network.

Refer Link below for EIGRP Documentation section for more details:

http://www.cisco.com/en/US/tech/tk365/tk207/tsd_technology_support_sub-protocol_home.html

Hope I am Informative.

PLS Use the Rating System available to Rate the Useful POST

Best Regards,

Guru Prasad R

mohmmad.imran · ‎05-02-2008

probably you need to enable the keepalive on the serial interfaces.

keepalive is the frequency at which the Cisco IOS software sends messages to itself (Ethernet and Token Ring) or to the other end (serial and tunnel), to ensure that a network interface is alive.

mohmmad.imran · ‎05-02-2008

probably you need to enable the keepalive on the serial interfaces.

keepalive is the frequency at which the Cisco IOS software sends messages to itself (Ethernet and Token Ring) or to the other end (serial and tunnel), to ensure that a network interface is alive. An interface is declared down after three update intervals have passed without receiving a keepalive packet.

Istvan_Rabai · ‎05-03-2008

Hi Manish,

I agree with Mohmmad.

Enable keepalive on the interface like this:

interface serial1/1

keepalive

This will set the keepalive to 10 seconds and your link can go down automatically, and the failover will occur.

Cheers:

Istvan

guruprasadr · ‎05-04-2008

HI All, [Pls Rate all Informative POST]

BFD feature (as told in my first POST] will be very helpful rather than configuring more Keepalive.

Configuring very close Keepalive values will normally pump the link with frequent keepalive packets.

Also, note the Keepalive packets are only Periodic Manner. You will have to wait until the timer value is arrived.

Pls Rate all Informative POST

Best Regards,

Guru Prasad R