First Hop Redundancy Protocol Comparison Essay

Protocol
Features

HSRP

(Hot Standby Router protocol)

VRRP

(Virtual Redundancy Router Protocol)

GLBP

(Gateway Load Balancing Protocol)

Router role– 1 active router.- 1 standby router.- 1 or more listening routers.– 1 master router.- 1 or more backup routers.– 1 AVG (Active Virtual Gateway).- up to 4 AVF routers on the group (Active Virtual Forwarder) passing traffic.- up to 1024 virtual routers (GLBP groups) per physical interface.
– Use virtual ip address.– Can use real router ip address, if not, the one with highest priority become master.– Use virtual ip address.
ScopeCisco proprietaryIEEE standardCisco proprietary
ElectionActive Router:
1-Highest Priority
2-Highest IP (tiebreaker)
Master Router: (*)
1-Highest Priority
2-Highest IP (tiebreaker)
Active Virtual Gateway:
1-Highest Priority
2-Highest IP (tiebreaker)
Optimization featuresTracking

yes

yes

yes

Preempt

yes

yes

yes

Timer adjustments

yes

yes

yes

Traffic type224.0.0.2 – udp 1985 (version1)
224.0.0.102-udp 1985 (version2)
224.0.0.18 – IP 112224.0.0.102 udp 3222
TimersHello – 3 secondsAdvertisement – 1 secondHello – 3 seconds
(Hold) 10 seconds(Master Down Interval)3 * Advertisement + skew time(Hold) 10 seconds
(Skew time)(256-priority) / 256
Load-balancing functionality– Multiple HSRP group per interface/SVI/routed int.– Multiple VRRP group per interface/SVI/routed int.Load-balancing oriented- Weighted algorithm.- Host-dependent algorithm.

– Round-Robin algorithm (default).

Requires appropriate distribution of Virtual GW IP per Clients for optimal load-balancing.(generally through DHCP)Requires appropriate distribution of Virtual GW IP per Clients for optimal load-balancing.(generally through DHCP)Clients are transparently updated with virtual MAC according to load-balancing algorithm through ARP requesting a unique virtual gateway.

* If the group VRRP Virtual IP on the master (higher priority) is the real IP configured on a different VRRP (Backup with lower priority) IOS will manage to make the VRRP router with the real IP, the master, by setting its priority to 255, knowing that the configurable range is [1-254].

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It can be useful to have some basic information about how the various First Hop Routing Protocols (FHRP’s) work. When I read that the first release of Cisco OTV (Overlay Transport Virtualization) requires manual FHRP filtering, I started wondering how I would do it. The Cisco documents talk about MAC address-based filters. Ok, to do that, you need some basic info. Hence this quick note with what I found.

Murphy’s Law applied: I looked for info for a while, found most of it, and then found a web page listing all the information (URL is at the end of this article). And I probably should have started with Wikipedia (it’s been pretty useful as a technical reference lately!)  My hope is that by repeating the info in one place it’ll be helpful.

OTV tip: The Cisco documents also mention that your FHRP gateway should not be on the OTV devices, i.e. the SVI (interface VLAN) must not be in a VLAN transported by OTV. One guess is that this is because manual or automatic FHRP hello/advertisement filtering won’t work on such an interface. The workaround if your Aggregation layer is the datacenter Layer 3 switch AND the OTV edge device is to do OTV in a separate VDC.

The promised info:

HSRP

Hello/advertisement: Sent to the general all-router multicast IP 224.0.0.2, UDP port 1985

Virtual MAC (VMAC) used: 0000.0c07.acXX, XX = HSRP group number in hex

http://en.wikipedia.org/wiki/Hot_Standby_Router_Protocol

VRRP

Hello/advertisement: Sent to dedicated multicast IP 224.0.0.18, IP sub-protocol 112

VMAC: 00-00-5E-00-01-XX, XX = the Virtual Router IDentifier (VRID),

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_vrrp.html#wp1054602

http://en.wikipedia.org/wiki/Virtual_Router_Redundancy_Protocol

GLBP

Hello/advertisement: IP multicast address 224.0.0.102, UDP 3222

VMAC: 0007.b4xx.xxxx

http://en.wikipedia.org/wiki/Gateway_Load_Balancing_Protocol

Overall

All of the above turned out to be at the following URL, with a bit more good summary info about how the protocols work:

http://routerjockey.com/2010/10/21/hsrp-vrrpd-and-glbp-compared/

Peter Welcher

Architect, Operations Technical Advisor

A principal consultant with broad knowledge and experience in high-end routing and network design, as well as data centers, Pete has provided design advice and done assessments of a wide variety of networks. CCIE #1773, CCDP, CCSI (#94014)

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