Saturday, October 8, 2016

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IPv6 First Hop Redundancy Protocol

                             Now in this topic let’s talk about IPv6 and ‘First Hop Redundancy”. First of all, do we even need a “First Hop Redundancy Protocol” with IPv6. Let’s take a look what IPv6 does for us by default. There is a native First Hop redundancy mechanism built in.
If we are in a topology like this.
                            And Routers R1 and R2, are configured for IPv6.They periodically going to send out an “ICMP Type 134 Packet”.
                    This is a “Router Advertisement”. Here you see that R1 is sending out a “Router Advertisement”.
                     In this case PC1 knows about its existence.
                       And some point R2 is going to do same thing, it’s gonna send a “Router Advertisement” out.
And when our PC hears that.
            it gonna say “Well i received the Router Advertisement, from R1 first”, and the as result that’s i am gonna uses my default gateway but if R1 ever goes down, then i receive this other “Router Advertisement” from Router R2 and I use it, but normally we gonna be using R1 as our default gateway to.
        Get out to the internet, however something happens to Router R1.
                   Then PC1 has learned via “Router advertisement” about Router R2, and it can start using Router R2 is a path out to the internet.
 And based on this default behavior of IPv6, we might ask do we even need to use something like HSRP with IPv6.Well we might, and reason say that “This failover, when PC1 is failing over from R1 to R2, that failover time might be on the order of 40 Seconds.
                                     And that’s quit bit of time to be down, and that might not be exceptional to our design, however we have most flexibility, we have the most ability to tune, what’s happening, if we do use a “First Hop Redundancy Protocol”, like seems that HSRP is most widely supported on our Cisco Devices. Let’s go out to interface, and see how to set it up.
HSRP Configuration for IPv6 on Router R1: -
Ø R1(config)#interface fastethernet 0/0
Ø  R1(config-if)#description CONNECTED WITH SW1
Ø  R1(config-if)#standby version 2
ü  One of big enhancement for HSRP version 2, was IPv6 Support. We want to make sure that, we running Version 2 of HSRP.
Ø  R1(config-if)#standby 10 ipv6 autoconfig
ü  We can obtain automatically. We could have a router use fastethernet 0/0. Link-local Prefix with EUI 64 to generate this link-local IPv6 address.
ü  That EUI 64 method of automatically constructing the IPv6 address, based on mac-address. EUI 64 is gonna be using the HSRP Virtual Mac-address to construct this IPv6 link-local address.
Ø  R1(config-if)#standby 10 priority 110
Ø  R1(config-if)#standby 10 preempt

HSRP Configuration for IPv6 on Router R2: -
Ø R2(config)#interface fastethernet 0/0
Ø  R2(config-if)#description CONNECTED WITH SW1
Ø  R2(config-if)#standby version 2
Ø  R2(config-if)#standby 10 ipv6 autoconfig
Ø  R2 (config-if)#standby 10 preempt

                      By the way i am showing you in this demonstration, how to set things up for HSRP for IPv6, if you want to setup GLBP for IPv6, if it supported on your devices. You would set it up in same way, that you set it up for IPv4, except when you specifying that Virtual Mac-address like I did here, with GLBP, i could said “glbp 10 ipv6 autoconfig”, but, remember GLBP doesn’t have the concern about setting it to version would also be similar with VRRP, but it seems that VRRP Support for IPv6, it’s not gonna be found as often as the other options in our Cisco gears.

Here our focus on HSRP for IPv6: -
Ø  R2#show standby brief
ü  You can see that, Router2 currently in the “Standby State”
ü  Preemption is enabled
ü  Priority is default 100
ü  And we can see the link local addresses, for the active HSRP Router IPv6 Address is “FE80::C801:DFF:FE3B:8” that’s Router R1
ü  Standby is local, and here is the Virtual IP Address “FE80:5:73FF:F8A0:A”, that’s we servicing, it’s the link local address, meaning that it’s valid on this network, which right now contains R1, R2 and PC1. Notice the Virtual IPv6 Address that end in “73FF:FEA0:A”.
 Now go to PC, again I got Router acting as a PC, and it’s automatically learning its default gateway information via “Router Advertisements”. Let’s see exactly, what it learned.
Ø  PC1#show ipv6 interface fastethernet 0/0

ü  First thing, i want to draw your attention to, is this “Default Router”, and it’s end with “73FF:FEA0:A:”, that’s the Virtual IPv6 address, and it is learned via HSRP for IPv6, with the assistance of “Router Advertisements”, the IPv6 address of the “default router”, and it should be able to ping IPv6 address, that’s on the internet.
Ø  PC1#ping ipv6 2004::1
ü  I didn’t configure default gateway on PC1, it was automatically learned via “Router Advertisements”

Let’s give couple of command on R1: -
Ø  R1#show standby brief

Ø  R1#show standby fastethernet 0/0

                            That’s the look at HSRP for IPv6, that’s gives us to ability to tune our “First Hop Redundancy”, and make that “First Hop Redundancy Failover”, happen more rapidly, then just relying on the “Router Advertisements”, that are built into the IPv6.

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