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Visitor
1994
Posts: 6
Registered: ‎09-16-2008
0

VRRP with single IP?

Unsure if this is a part of the VRRP spec, or Juniper's implimentation. All config examples I can see for VRRP show at least two IP's being used. Always a 'real' ip and a virtual-address. I'm looking to impliment VRRP on some J-series for many /28s and /29s. in some casess, /30. From what I can tell, it's not even possible on a /30 as you'd be using both available IPs for the routers. Here's a sample config which would show that no non-router IP'sare possible



unit 200 {
vlan-id 200;
family inet {
address 10.170.3.185/30 {
vrrp-group 0 {
virtual-address 10.170.3.186;
}
}
}
}

 

Is this the only way VRRP can be implemented? Any other way that I can create gateway redundancy to hosts without requiring their routing tables to be updated? This is on a J2350.

 

 

Super Contributor
AntonD
Posts: 111
Registered: ‎11-07-2007
0

Re: VRRP with single IP?

No. What you want to do is not possible. You will always need a minimum of 3 IP address to setup VRRP. 1 for the local router, 1 for the remote router and 1 virtual IP address. The is the fundemental way in which VRRP works. You will therefor always have to have a /29 a the minimum subnet size. A /29 will also allow 3 additional hosts on the subnet. A /30 will not work.
Visitor
1994
Posts: 6
Registered: ‎09-16-2008
0

Re: VRRP with single IP?

Bummer. Any VRRP alternatives? I was used to Carp on OpenBSD/FreeBSD where one could have *just* the virtual IP. Or, any kludge where the virtual ip exists outside of the 'real' ip where I could RFC1918 IP's for the 'real' IPs just to have them there? I'd think not since the virtual-address seems to imply a /32.

Super Contributor
GuyDavies
Posts: 93
Registered: ‎09-26-2008
0

Re: VRRP with single IP?

Actually, you *can* do VRRP with just two addresses.  This makes use of the real address from the master as the shared address.  As such, the master always must be master when it is live.  It is preemptive so it will force itself to be master when it comes back online.  If you do this, it may break interface tracking because you're trying to override the requirement that the master interface is always master while it is alive.

 

This isn't necessarily what you're after but it is a way of doing VRRP without three addresses. 

 

Rgds,

 

Guy 

Visitor
dr_olive
Posts: 4
Registered: ‎11-05-2008
0

Re: VRRP with single IP?

I would not use a vrrp alternative since vrrp is a widely-deployed standard and an alternative proto would be non-standard.  What is the reason for needing a /30 and not being able to use a /29?

 

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