Single IP multiple Devices

[salemmahara]

Hello guys

I'm interested to know your ideas to solve this problem:

Imagine, we are going to connect our branch to Head quarter or a service provider or .... and its MPLS or VPLS or P2P connection. We only have one IP address. But after a while, we'll find this connection sooooo important, then we start to find a way to cover the case where our edge router would fail. So we decide to buy another router. Here the question comes. Where should I set the only available IP? FHRP is not a good idea at edge ( Although we don't have 3 available IP address , but we can use 2 other IP and change the subnet mask! _ This solution is not good and looks even illegal to use IP which aren't ours).

Note: HQ or service provider has no upcoming plan to add another link to increase redundancy.

Note: Our edge device can be ISR 4000 or ISR 1000 or ISR G2

[Jon Marshall]

If you buy another router buy some more IPs or just have the spare router configured and ready to power up. 

If there are public IPs definitely do not use IPs that do not belong to you. 

Jon

[salemmahara]

Hello Jon

Thank you for replying

Although it's a working solution, but I'm looking for a bit more flexible one. Automatic at bone actually.

[Georg Pauwen]

Hello,

I guess you could use HSRP and configure the same IP address on both WAN interfaces, as long as one of the interfaces is shut. Based on the state of the active or standby router, an EEM script would shut/no shut the interface so that at any given time, only one WAN interface would be active.

Below is what I have in mind (the attached PNG shows the suggested topology):

R1

interface GigabitEthernet0/0
description Link to ISP
ip address 100.100.100.1 255.255.255.252
!
interface GigabitEthernet0/1
ip address 192.168.1.1 255.255.255.0
standby 1 ip 192.168.1.3
standby 1 priority 110
standby 1 preempt
!
ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0
!
event manager applet ISP_FAILOVER_DOWN
event syslog pattern "Active -> Init"
action 1.0 cli command "enable"
action 2.0 cli command "conf t"
action 3.0 cli command "interface GigabitEthernet0/0"
action 4.0 cli command "shut"
action 5.0 cli command "end"
action 6.0 cli command "clear arp"
action 7.0 cli command "clear ip nat translation *"
!
event manager applet ISP_FAILOVER_UP
event syslog pattern "Listen -> Active"
action 1.0 cli command "enable"
action 2.0 cli command "conf t"
action 3.0 cli command "interface GigabitEthernet0/0"
action 4.0 cli command "no shut"
action 5.0 cli command "end"

R2

interface GigabitEthernet0/0
description Link to ISP
ip address 100.100.100.1 255.255.255.252
!
interface GigabitEthernet0/1
ip address 192.168.1.2 255.255.255.0
standby 1 ip 192.168.1.3
standby 1 priority 100
!
ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0
!
event manager applet ISP_FAILOVER_UP
event syslog pattern "Standby -> Active"
action 1.0 cli command "enable"
action 2.0 cli command "conf t"
action 3.0 cli command "interface GigabitEthernet0/0"
action 4.0 cli command "no shut"
action 5.0 cli command "end"

!

event manager applet ISP_FAILOVER_DOWN
event syslog pattern "Active -> Speak"
action 1.0 cli command "enable"
action 2.0 cli command "conf t"
action 3.0 cli command "interface GigabitEthernet0/0"
action 4.0 cli command "shut"
action 5.0 cli command "end"
action 6.0 cli command "clear arp"
action 7.0 cli command "clear ip nat translation *"

[salemmahara]

Hello Geurg

What's up dude?

Thank you for continues effective and helpful support here.

This EEM solution is a perfect choice but there are still some problems. First of all, we have a couple of ISR 1800 and this is the point where the problem starts ! It's not supported (I've just realized the tag is missed from the topic. It's probably rejected when I was creating the topic).

on the other hand, I'm interested to find whether there's another method. I mean, is it possible to handle it using routing protocols or .... .

[Georg Pauwen]

Hello,

EEM is not supported on the ISR 1800 ? Which IOS version are you running ?

[salemmahara]

Hello again

It's 12.x !

I don't have any service contract and when I check Cisco Software website, it doesn't allow me to download last IOS files. Is there any other way to to have these files?