Configuring Redundancy on 3 LINKS

[okoroji80]

What i want to achieve:

1. User 1,2,and 3 will be accessing the server resource from different locations

2.  User 1, will use link A as its Primary link, B as secondary, C as  tertiary such that in the event of A failing it will automatically  switch over to B. IF B fails it will use link C.

3. The scenario 2 above is applicable to user 2 and 3

[John Blakley]

It would help if you could tell us what the links are. What type of connection are they? Are they same or different ISPs? What routing protocol?

HTH,
John

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[okoroji80]

Thanks Mr. John,

the three links are all different links (ISP)

No routing protocol ,only static routes

the issue is on how to setup the 3 or more users to failover the 3 linsk automatically

eg:

ip route 1.1.1.2 255.0.0.0 4.4.4.3 track 15

ip route 1.1.1.2 255.0.0.0 3.3.3.2 5

ip route 1.1.1.2.255.0.0.0 2.2.2.1 10

User1 Ip:1.1.1.2 Gw 1.1.1.1

user2 ip:1.1.1.3 Gw 1.1.1.1

User3 ip:1.1.1.4 Gw 1.1.1.1

[blau grana]

Hi Jude,

It looks like all three users are from same subnet. I think that PBR should do the job.

Best Regards

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[paul driver]

Hello

First of all this is a duplicate posting but its just been renamed so can you please close one of them

https://supportforums.cisco.com/thread/2263023

Regarding you query:

Try using ip sla to track your router interfaces

From R2 perspective (if i have the ip addressing corect) -  Also this will then need to be duplcated on R1 but obvisouly the addressing needs to be change to accomodate.

Ip sla 1

Icmp-echo 2.2.2.1 source-ip 2.2.2.2

Freq 5

Timeout 2000

Ip sla scheduled 1 start now lifetime forever

Ip sla 2
Icmp-echo 3.3.3.2 source-ip 3.3.3.3
Freq 5
Timeout 2000
Ip sla scheduled 2 start now lifetime forever

Track 1 rtr 1
Track 2 rtr 2

ip route 10.1.1.2.255.0.0.0 2.2.2.1 250 track 1

ip route 10.1.1.2 255.0.0.0 3.3.3.2 251 track 2

Ip route 10.1.1.2 255.0.0.0 4.4.4.3 252

Res
Paul

Sent from Cisco Technical Support iPad App

[okoroji80]

thanks.

that means i should have three (3) sets of IP SLAs for the three  (3) Users ?

sorry, i did not get the comment you made above '' it should be duplicated on R1''

or could you please  highlight more on the comment above "

From R2 perspective (if i have the ip addressing corect) -  Also this  will then need to be duplcated on R1 but obvisouly the addressing needs  to be change to accomodate. ""

thanks

[blau grana]

Hi Jude,

I dont think Paul's solution is correct. Yes, it offers redundancy but host A, B and C will always use same link. If all links are working all hosts will use link A, if A fails they will use link B and link C will be last option.

As I understand your request, you want each host use different link if all links are working and each link will be backup for other links from user's point of view.

I think this can be done only with Policy Based Routing.

Best Regards

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[okoroji80]

Hi Blau,

you got the point quite correct.

could you please help with the config to achieve this .

[blau grana]

Hi Jude,

this should do the trick, I didnt see IP plan in your diagram so I just made up my own. This PBR configuration should work regardles of your routing configuration.

10.0.0.0/24 - subnet where three hosts reside

10.255.255.10/24 - ip address of server

       .1   10.10.10.0/24   .2 -

R1 - .1   10.20.20.0/24   .2 - R2

       .1   10.30.30.0/24   .2 -

R1 configuration

interface XYZ

description link to server

ip address 10.255.255.1 255.255.255.0

ip policy route-map RM_PBR

!

ip access-list extended HOST_A

permit ip host 10.255.255.10 host 10.0.0.1

ip access-list extended HOST_B

permit ip host 10.255.255.10 host 10.0.0.2

ip access-list extended HOST_C

permit ip host 10.255.255.10 host 10.0.0.3

!

route-map RM_PBR permit 10

match ip address HOST_A

set ip next-hop 10.10.10.2 10.20.20.2 10.30.30.2

!

route-map RM_PBR permit 20

match ip address HOST_B

set ip next-hop 10.20.20.2 10.30.30.2 10.10.10.2

!

route-map RM_PBR permit 30

match ip address HOST_C

set ip next-hop 10.30.30.2 10.10.10.2 10.20.20.2

R2 configuration

interface XYZ

ip address 10.0.0.254 255.255.255.0

ip policy route-map RM_PBR

!

ip access-list extended HOST_A

permit ip host 10.0.0.1 host 10.255.255.10

ip access-list extended HOST_B

permit ip host 10.0.0.2 host 10.255.255.10

ip access-list extended HOST_C

permit ip host 10.0.0.3 host 10.255.255.10

!

route-map RM_PBR permit 10

match ip address HOST_A

set ip next-hop 10.10.10.1 10.20.20.1 10.30.30.1

!

route-map RM_PBR permit 20

match ip address HOST_B

set ip next-hop 10.20.20.1 10.30.30.1 10.10.10.1

!

route-map RM_PBR permit 30

match ip address HOST_C

set ip next-hop 10.30.30.1 10.10.10.1 10.20.20.1

Best Regards

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[okoroji80]

....But do i still need the ' ip route with tracking on the router , or the PBR above is all that is needed ?

[blau grana]

of course you still need to configure ip routing (static routes with tracking or IGP, lets say OSPF with different cost for each link). PBR will only take of specific traffic matched by ACLs referenced in route map.

Best Regards

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[okoroji80]

Ok.

Basically i have this also configured in addition to the IP SLA

USER1

=======

ip route 1.1.1.2 255.0.0.0 4.4.4.3 track 15

ip route 1.1.1.2 255.0.0.0 3.3.3.2 5

ip route 1.1.1.2.255.0.0.0 2.2.2.1 10

USER 2

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

ip route 1.1.1.3 255.0.0.0 3.3.3.2 track 20

ip route 1.1.1.3 255.0.0.0 2.2.2.1 15

ip route 1.1.1.3 255.0.0.0 4.4.4.4 10

USER3

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

ip route 1.1.1.4 255.0.0.0 2.2.2.1 track 30

ip route 1.1.1.4 255.0.0.0 4.4.4.3 25

ip route 1.1.1.4 255.0.0.0 3.3.3.2 15

  IP SLA

User1 IP SLA

------------

ip sla 15

icmp-echo 4.4.4.3 source-ip 4.4.4.4

timeout 120

threshold 100

ip sla shedule 15 life forever start-time now

track 15 rtr 15

track 15 ip sla reachability

User2  IP SLA

Let me know if the IP SLA is not needed ?

thanks.

[blau grana]

Let me know if the IP SLA is not needed ?

The answer is, it depends. What type of links do you have between R1 and R2? Lets say if link A fail, will line protocol on matching interfaces go down? If not corrupted next-hops will stay in routing table so PBR will still use them and traffic will be blackholed.

IP SLA is good solution to track reachability of next hops if or you can some other workaround.

Do you use these links only for traffic between server and specific hosts or it will also be use to transport some other traffic, what routing protocol do you use in your domain?

Best Regards

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[okoroji80]

.... Yes for Server and specific hosts

----- No routing protocol in use for now. just the static routes.

thanks

[blau grana]

ok, if these three links are dedicated only to traffic between server and three hosts, PBR should do the trick. In other thread you mentioned that cat6 cable connect R1 and R2 routers IP SLA should be used to verify next hops reachability.

Best Regards

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