Floating static

Unanswered Question
Jun 12th, 2007

Hi, I have design my lab as below:

R1------

|

|--R3 --- Server (10.10.10.0/24)

|

R2------

R1 is primary and R2 is backup for incoming traffic. Outgoing from server

is using HSRP. I configured static route at R1 and R2.

R1: ip route 10.10.10.0 255.255.255.0 172.16.1.1

R2: ip route 10.10.10.0 255.255.255.0 172.16.1.1 200

If interface at R1 facing to R3 is down, R1 still advertised 10.10.10.0/24, thus server will not reachable. Even R2 has same static route with higher AD (backup puspose), it will not advertise 10.10.10.0/24 route as R1 still alive.

My question, how can i solve this problem other then using dynamic routing.

I just want to use static route. Is there any method if the router saw attached interface is down, it will withdrawal route and let other router advertise the routes?

Thanks,

-mazlan

I have this problem too.
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CSCO10892433 Tue, 06/12/2007 - 19:52

Hi mazlan

Floating static is not an adquate solution for this senario. What you should do is to use the standby track serial command. for example

On R1

int fa0/0

standby 1 track serial0/0

On R2

int fa0/0

standby 1 track serial0/0

This command give the HSRP group the capability to track the serial interface and when the serial interface of the primary router goes down, the backeup router will take over as the primary router and the traffic wiil not be lost.

HTH

SSLIN

CSCO10892433 Tue, 06/12/2007 - 21:24

Hi Narayan

Thanks for your update and sorry if I mislead something. I think I should study hard on this new features I've never learned before. Thanks for the link too.

Best Regards.

SSLIN

rmujeeb81 Tue, 06/12/2007 - 23:02

Hello Narayan,

I want to ask a question related to Object Tracking feature.As I understand this feature will provide exit for outbound traffic by keeping track of interface status but what will happen if a router having 2 internet connections with 2 ISPs and a server is located at LAN. Users access that server from internet so in that case Object Tracking reliably inject backup route into routing table in case of primary link failure but what would happen for inbound traffic towards server.

Another thing is that customer will get public ip addresses for server publishing on internet so if there are 2 ISPs they will assign ip addresses from their pool so in that case customer will have to change public ip address of sever ( might be statically NATed ) and again same problem will occur ( inbound traffic shifting ).

Regards,

Mujeeb

royalblues Tue, 06/12/2007 - 23:17

Mujeeb,

In case of internet connections, your visibilty is only till the last mile to your ISP. so when one of the last mile goes down, you can always have the traffic shifted to the backup ISP.

When this goes out to the internet, this will get Natted to the Pool provided by ISP2 and hence inbound traffic will also be through that ISP. All you need to care is whenever the packet hits the ISP2 router it should carry the source from the ISP pool

The best way is to have your own IP block (from APNIC/ARIN) as it becomes routable by every ISP.

HTH, rate if it does

Narayan

rmujeeb81 Wed, 06/13/2007 - 03:17

Hello Narayan,

Thanks for your response.You are right that inbound traffic will be dependent on NATted pool if client is doing overloading through outgoing interfaces but if client is using Static NAT for a server publishing then client has to change that NAT statement manually.

As you mentioned the other solution could be to get portable ip pool from RIR.In this case cutomer could get AS number from RIR and do BGP multihoming with both ISPs.

Let consider a scenario in which customer have 2 internet connections to same ISP for redundancy and want to use static routing(no BGP) then Object Tracking will provide reliability for outbound traffic only. What should be done for inbound ??

Regards,

Mujeeb

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