Internet Routing with BGP, my new e-book, is now available from Amazon, Apple and Google

▼

The book is now available through Amazon in Kindle format, Apple Books in EPUB format and the Google Play Store in PDF and EPUB formats. The price is US$ 9.99 or € 9.99 (or similar in other currencies).

The PDF version has the best formatting, so I recommend that version if you're reading on a computer with a relatively big screen. The EPUB version is also good, but you may have to change the font size and/or sometimes rotate your reader to landscape for the router output examples to show properly. With the Kindle version, that output looks a bit different.

Book description:

The internet is “a network of networks”. It's made up of tens of thousands of largely independent networks, but somehow the users of one network can communicate with the users of any of the other networks. The Border Gateway Protocol (BGP) is the glue that binds these disparate networks together.

BGP is a routing protocol: its main job is to allow each network to learn which ranges of IP addresses are used where, so packets can flow along the correct route.

However, BGP has a more difficult job to do than other routing protocols. Yes, it has to make the packets reach their destination, but BGP also has to pay attention to the business side: those packets only get to flow over a network link if either the sender or the receiver pays for the privilege.

This book covers the fundamentals of the technical side of BGP, and also looks at the intersection between the technical and business aspects of internet routing.

The book contains 40 configuration examples that readers can try out on their own computer in a “BGP minilab”.

You can read several sample chapters in PDF format or as an EPUB e-book.

The book is also available directly from me as a site license.

Full details at the book description page.

Permalink - posted 2022-11-18

Free Range Routing vs Quagga/Cisco

▼ Back in the 1990s, I used Cisco routers. Mostly rather underpowered ones such as the Cisco 2500 series. I later started using the Zebra and then Quagga routing software for the lab part of my training courses.

However, like Zebra before it, Quagga also ran out of steam but was forked by people (and companies) who saw value in the software. The Quagga fork is Free Range Routing a.k.a. FRRouting a.k.a. FRR.

As I was writing my new BGP book, I made configuration examples using Quagga. But about two thirds in, I decided to switch to FRRouting. This had the huge advantage that I could include RPKI examples. But on the other hand, I now had to revisit all my earlier configuration examples to see if they still worked under FRR. And too often, the answer was "no".

So let me list some differences between Quagga or even old school Cisco routers and FRRouting.

A really annoying change is that in FRR, it's no longer "ip as-path ..." but "bgp as-path ..." to define AS path access lists. Yes, it makes more sense. But this change immediately makes it impossible to have a configuration file that works on both Cisco/Quagga and FRR. Same thing for "ip community ..." vs "bgp community ...".

I think the solution here would have been to accept the "ip ..." syntax and translate that into "bgp ..." syntax. That way, an FRR BGP daemon could still read Quagga BGP daemon configurations and work as expected.

Another change is that with FRR, there's no way to get around "address-family ipv4".

Way, way, way back in the day, we didn't have IPv6. Actually, it took quite a while for 1990s routers like the 2500 series to gain IPv6 capability. So there was no reason to differentiate between BGP configuration commands that both apply to IPv4 and IPv6 and configuration commands that only apply to either IPv4 or IPv6.

With Cisco routers, you could always just pretend like IPv6 didn't exist and enter configurations like:

!
router bgp 65086
 no synchronization
 network 10.86.0.0 mask 255.255.0.0
 neighbor 203.0.113.83 remote-as 65083
 no auto-summary
!

On FRR, you can still paste that configuration snippet. But if you then issue "show running-config", this is what you get back:

!
router bgp 65086
 neighbor 203.0.113.83 remote-as 65083
 !
 address-family ipv4 unicast
  network 10.86.0.0/16
 exit-address-family
exit
!

Yes, it boils down to the same thing, but it looks rather different. Especially as the configuration gets longer and the non address family part and the IPv4 address family part don't fit on the screen at the same time.

Bottom line: FRR is moving away from the traditional Cisco configuration language relatively quickly, white Quagga, for BGP at least, stayed pretty close to that. So moving from Quagga to FRR is a bigger step than you might think.

Also, as much as we may be unhappy with Cisco for some of their high profile software bugs, more minor software bugs happen much more frequently in these software implementations such as Quagga and FRR. For instance, I find myself not being able to use ^(64496_)+$ to match one or more instances of AS 64496 in an AS path but nothing else. However, ^(_64496)+$ does work as expected.

Permalink - posted 2022-11-02