VRRP

Peter H. Schmidt writes "As the world increasingly relies upon the Internet and TCP/IP-based networks, their reliability and availability have become pressing topics for both enterprises and service providers. The Internet was designed for resiliency, not the 99.999% uptime of the PSTN, but it is now being required to do both jobs. This book on VRRP -- the Virtual Router Redundancy Protocol -- details the open, RFC-track protocol which has been developed to help ensure that edge router failures can be handled automatically without affecting connectivity." Peter's complete review (below) is interesting even if you never have to deal with the network at this level. VRRP Increasing Reliability and Failover with the Virtual Router Redundancy Protocol author Ayikudy Srikanth, Adnan Adam Onart pages 540 publisher Addison Wesley rating Recommended reviewer Peter H. Schmidt ISBN 0201715007 summary An in-depth review of VRRP that is loaded with helpful and informative details.

Protocols that allow for automatic failover to a backup router have been around for a while, but they are proprietary, including Digital's IP Standby Protocol (IPSTB) and Cisco's more well known Hot Standby Routing Protocol (HSRP). These protocols have been used successfully for years, but as with all proprietary protocols, they lock users into one vendor. Plus, the test of time has shown there are ways in which they can be improved upon. VRRP has been developed in response.

VRRP lets you set up groups of routers to cover for each other, with each group acting like one virtual router with it's own MAC and IP addresses. If the main router in a group should go down, the others will quickly (in under 3-4s, typically) notice and one of them will be elected to take over. VRRP makes it easy to set up multiple routers with multiple WAN connections and make sure that WAN connectivity won't be lost if a router goes down.

As the open alternative to HSRP, you can count on VRRP being widely supported by the router vendors. Even Cisco is shipping it now. If you design, build or install routed networks of any size, VRRP is something you probably need to learn about.

Read This Book!

Let me just say up front that I think this is a very good book, and worth the read. As the title says, it is all about how to increase the reliability and failover capability of your network. VRRP is its subject, but it is treated with a thoroughness and attention to context I have rarely seen in a protocol text. Perhaps that follows from the fact that reliability and availability are only of concern due to economics; few protocols are developed to meet a business need, so most books on them never need to get beyond defining where they fit in their protocol family. Despite the context material, I found it easy to jump to the low-level technical details, yet was somewhat surprised to find myself actively enjoying the extensive introductory material.

Srikanth and Onart have put a wealth of background into the book. The first chapter treats network availability from a theoretical perspective, but does it so clearly and enjoyably that I read it straight through and felt I had learned some valuable new concepts. It also gave me all the context necessary to easily follow their discussion of the need for, conceptual operation of, and benefits from VRRP in Chapter 2.

Part II, comprising Chapters 3-6, presents the protocol, discussing its messages, state machine and issues with different LAN technologies, firewalls, tunnels and VPNs. I found this a useful complement to the RFC. Here is where I found the details I always look for first when confronting a new protocol: how many messages are there, how many states, what kind of implementation trade offs are going to be necessary? I particularly appreciated the abundance of clear, annotated diagrams in this part of the book, though they aren't confined to these chapters alone.

The chapters of Part III concern themselves with managing VRRP, and what is noteworthy here are the numerous examples of how you can configure and manage realistic scenarios. Juniper and Nortel routers are used in the examples, and you are given step by step instructions on using SNMP, the CLIs and a GUI (HP Openview). If I had to set a customer up with a redundant router configuration tomorrow, I would grab these chapters first thing.

Part IV may be the most useful part of the book for the experienced network engineer. Chapter 10 presents an excellent discussion of the pros and cons of VRRP vs HSRP and IPSBP, and includes some nice summary tables. Chapter 11 discusses the future of VRRP, and answered many of the niggling "How would it handle this scenario?" questions which had popped up as I read how the current VRRP works.

The final section of the book is comprised of 200 pages of appendices. They start with a moderately brief but well done overview of TCP/IP and IP networks. That is followed by the complete VRRP MIB. Then we are given Linux source from http://w3.arobas.net/~jetienne/vrrpd/ and a nice commentary on it. Next is a thorough explanation of the SDL (Specification and Description Language) and flowcharts which were used to define the state machine in Part II. And if this isn't enough rigor for you, you'll be pleased that the following appendix using first-order predicate calculus to specify VRRP yet more clearly. (If you don't know what first-order predicate calculus is, just feel lucky and skip that part...) The final appendix covers UML, the Unified Modeling Language, which also is used in Part II to show how VRRP state transitions occur.

What's Not to Like?

There is very little to object to about this book. If it has a fault, it may be that it is a bit too comprehensive. VRRP is actually a fairly simple protocol, and I write that as someone who has designed and implemented protocol stacks for over 8 years. The level of rigor and detail put into VRRP in this book are worthy of something as hairy as OSPF or BGP4. I found myself getting lost in the notational details of their examples at times, they were so exactingly detailed, but I found that if I just looked at the diagram and skipped to the last paragraph, I'd get what I needed. This book would actually make a pretty good reference book on networking in general, there's so much here!

FAQs

What level of experience is needed to make good use of the information in the book?

This book has all the intro material a novice to networking could want, yet has it all so well organized that it is easy for the advanced reader to find the interesting details.

Who will find it most useful? Is there an existing, canonical book that already covers the same ground?

I think this book would be most useful for enterprise network designers, implementers and operations people, no matter what their current skill level. I couldn't find another book on VRRP, so it's good that the only game in town right now is a good book.

Is the book readable as well as technically accurate? Is the language stilted, or natural? Are examples easy to follow?

The book is very readable - unusually so. As for accuracy, I didn't notice anything amiss, and I used to QA stuff like this. Good use of language, and a ton of excellent examples.

Is the depth appropriate?

This book dives deep, but not without plenty of warning and acclimatization first for people not quite ready for the open ocean.

Are the illustrations appropriate and well executed?

Excellent, clear illustrations.

Do any extras come with the book, like a CD-ROM of additional information or code samples?

You get a full printout of the VRRP MIB, as well as commented source code.

What's missing from the book? Would it benefit from illustrations, a better index, a final chapter on practical applications?

Nothing significant.

You can purchase VRRP from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

Router problems

[defile]

In my experience, downtime is caused more by router misconfigurations and not physical problems: peer router broadcasts bad information and takes down a network, admin discovers that the backup route wasn't configured properly at all, admin reboots a set of routers only to find that the TFTP server hosting the OS hasn't been running for 3 months, etc. :)

The protocol seems like it will do nothing to address this. However, physical outages do tend to last longer than misconfiguration outages, so this protocol may help yet.

Re:Router problems

[mosch]

I have significant experience with VRRP and can attest that it's a Good Thing(tm). I've used it on border routers, on load balancers and on SSL accelerators, and it's incredibly useful not just for preventing unplanned downtime, but it also makes it easy to fail to a second router, upgrade the primary router, then cut back to the primary router and upgrade the secondary router without ever having downtime.

And honestly, if you're having significant problems due to router misconfiguration, you should really consider replacing your network staff. A few glitches are to be expected, but if they're causing more downtime than your hardware, perhaps they need to study up before they're allowed near your production kit.

good review

[haa...jesus christ]

what's up with all the good book reviews on slashdot lately? well-written, to the point, etc. - what gives? :)

hmm

[stratjakt]

>> If it has a fault, it may be that it is a bit too comprehensive.

This is awful!

How can I look down my noses at the others in my office with the air of superiority that comes with understanding more of the geeky technicalities of our computer system than they do?

If they keep writing technical books that people can understand, we'll all be relegated to memorizing the stats on Pokemon playing cards!

Burn this book. It's a witch I tells ya.

Not Open enough for OpenBSD

[ostiguy]

Cisco maintains patent encumberances upon VRRP - if you use/sell VRRP, and get into a completely unrelated patent/licensing/whathaveyou war with Cisco, Cisco maintains the right to seek damages for your use of VRRP.

I have come to see the merits of this position (dhartmei@ makes a good case, btw ;-) ) . The OpenBSD guys have been sitting on a VRRP package for *years* that they cannot include because this is not really an open standard.

Why does Cisco do this? It may be that they are pissy because HSRP wasn't accepted as the standard. Or they might be looking for protection as they might be afraid other people could have patent claims against stuff that might underlie VRRP - and thus these encumberances could allow them to enact a legal war of attrition as each side has competiting patent claims that would ensure deadlock.

ostiguy

No Open Source implementation because of Patent?

[gehirntot]

From reading the web, it seems that no open source implementation is possible unless a license has been obtained from Cisco.

I am not aware of any open source project that has ships VRRP. The IETF has received more information from Cisco about their Intellectual Possession in regards to VRRP.

Publisher's site/sample chapter.

[gatekeep]

Here's the publisher's page on this book. It even includes a sample chapter.

Enjoy

[ More Pages Like This ]

[ekrout]

Home Web page of the VRRP working group :: http://www.ietf.org/html.charters/vrrp-charter.htm l

VRRP Internet draft :: http://www.ietf.org/internet-drafts/draft-ietf-vrr p-spec-v2-06.txt

VRRP for IPv6 :: http://www.ietf.org/internet-drafts/draft-ietf-vrr p-ipv6-spec-03.txt

VRRP RFC :: http://www.ietf.org/rfc/rfc2338.txt

Email the chair of VRRP :: mailto:Mukesh.Gupta@nokia.com

Mailing list archive :: ftp://ftp.ietf.org/ietf-mail-archive/vrrp/*

VRRP OpenSource code

[andi_nip]

I am very VERY surprise that nobody is talking about Keepalived (www.keepalived.org). This is the most advanced VRRPv2 code available in the OpenSource community. In addition it extend VRRPv2 rfc with a synchronization instances code that is very usefull for making persistent routing path. many extensions available.... Keepalived is wonderfull code after 2 years of debugging it is now STABLE and ready for production. the old code from jerome etienne is very draft and really not secure... look at Keepalived if you want to play with VRRP on linux.

Reliance on Secondary Routing Protos...

[jcostom]

I work for Nokia, though don't speak on behalf of the company.

One problem with VRRP v2 as it stands today. Imagine a case where you have two parallel routers and are running VRRP. If you experience an interface failure on your primary router. Ok, that interface fails over to the secondary unit. Since you only experienced an interface failure (let's suppose this is a pair of edge routers), say on the outside. Because the inside i/f of the router is still up, you need a secondary routing protocol to direct the traffic to the secondary router - introducing an asymmetric routing condition. This is easily done with OSPF.

Consider the case, however, that we're no longer talking about routers, but instead firewalls. This condition can wreak havoc with your firewalls state tracking mechanism if your firewall's connection state tracking mechanism is either not shared with the redundant unit, or your connection is fast enough that reply packets arrive before connection data is sync'd.

Enter extensions to VRRP like VRRP Monitored Circuits (aka VRRPmc), from Nokia. If you're running Nokia firewalls (which run Check Point for those who don't know), you're probably using VRRPmc.

When you configure VRRPmc, you monitor the other interfaces in use for VRRP. If one of those other interfaces goes down, you decrement your VRRP priority value by a pre-defined delta value, which if you've calculated correctly, will cause the primary unit to begin advertising VRRP priorities that are lower than what the secondary unit is advertising, thereby causing the virtual ips/macs to shoot over to the secondary unit, rather than just the i/f that failed. On the wire, it still looks like good old VRRP. I'd like to see either the monitored circuits method, or something similar implemented in the mainstream VRRP protocol.

VRRP isn't the end-all-be-all

[netwiz]

I've run into countless failure scenarios where VRRP ends up being mostly useless. Scenario one where the gateway segment and server segements don't both fail simultaneously is one, where the primary stays up on the front end, but the server segment fails over.

Also, there's the issue of the L2 packets being broadcast, so that when the switch you're connected to stops forwarding unicast (oh, but broadcast and multicast still work just fine, thank you very much), VRRP is pretty much useless. It'll never realize that something's gone horribly wrong, and that failing over is necessary.

I guess my point is that most of the "automated failover" solutions out there either are or have been pretty much worthless given the failures I've seen, and that VRRP, for all it's good points, only covers about ten percent of failure situations. For straight up gateway reachability, it does just fine (in fact, it's a nearly complete rip of Cisco's HSRP, altho I'm not exactly sure of the timeline for each protocol), and in fact it's a superior solution in that regard, but for anything else other than L3 gateway services where all you're doing is plain-vanilla IP routing, it's pretty lousy.

What I'd like to see is a unicast-based, fully-configurable hot-standby solution. Something where you're forced to enter the IP of the other partners in the redundancy group. Simply sticking to broadcast- or multicast-based solutions isn't going to cut it in a fully switched environment. Granted, the above is going to require a bit more configurationbut come on, it would add what, one, maybe two lines to each configured group? Hell, my environment has two hundred configured interfaces like this, and I'd put up w/ the extra work if it would have saved me from some of the failures I've had.