The Winning that is Digital Optical Monitoring (DOM)

A number of Cisco Optical Interfaces implement Digital Optical Monitoring (DOM) which enables the monitoring of some interesting status values on the interface with the most useful values being the optical receive and transmit powers.

By being able to monitor transmit and receive power levels of optical interfaces you are able to characterise the fibre loss and isolate any unidirectional connectivity issues.

The following link is useful for identifying which optical interfaces support DOM –

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From Scratch #4: Configuring an OSPF Virtual Link

Today we are going to configure an OSPF Virtual Link.

What is it?

Before we answer what it is, take a step back and look at one of the basic requirements of OSPF. That is, all areas must be connected to the backbone area (area 0). A virtual link gives us a way around that requirement.

If for some reason, you are stuck with a topology where you must connect a non-zero area via another non-zero area you can create a virtual link between the ABR in non-connected area to a router in area 0. That will hopefully make a bit more sense in a few minutes.

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Traceroute ain’t tracert

After ping, trace route is probably one of the most common network tools. Be it for fault finding, verification, discovery or testing. Between ping and trace route you can do a lot. Trace route, at it’s most basic sends a series of packets with an ever increasing Time to Live (TTL), starting at TTL=1. Every layer 3 device in the path will decrement this TTL and send a TTL Expired back towards the source if the TTL hits 0, until eventually the packet has a TTL that is long enough that it will reach the end device. The series of returned TTL Expired packets will tell you the path that the packet took.

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New tech: ISR4451-X, 6800

Discovered a couple of new bits of Cisco equipment last week. The ISR 4451-X and the 6800 series switch. Actually I lie, Bruce noticed them and sent me an email. But anyway, they sound interesting.

ISR 4451-X

The 4451-X is positioned somewhere above the existing upper end ISR G2s and below an ASR1001. It runs IOS-XE which we can pretty much expect from all non-SP equipment these days. The pricing sits in a similar range, the quote I got from my reseller was a few thousand above a 3945 and a few thousand less than a ASR1002. Note I was just looking at the chassis and IOS; no extra PSUs or interfaces etc.

This device seems to fit in a high intensity WAN end-site/large remote office. I don’t see myself buying any in the near future, but they fill a nice hole in the existing ISR-G2 range.

Catalyst 6800 Series Switches

This I found far more interesting. Firstly, I wasn’t really expecting anything in this space. Don’t know why, the 6500-E series chassis are now about 8 years old. But on the other hand the SUP-2T is only 2 years old. I expect (or is it hope?) that Cisco will support the 6500s for some time yet.

The new 6800 comes in some different sizes to the old 6500s, from smaller form factor aggregation units 6880-Xs and larger 7-slot chassis 6807-XL. I assume there will be other sizes later.

They offer Cisco’s SDN (onePK) for those who are interested, and LISP and VPLS. LISP I am quite keen to give a try, the VPLS I am just curious if it will actually work this time.

What’s really interesting is the 6800ia – which looks like a Nexus-2000-type-FEX-for-the-campus. The ability to have a single (well, probably dual) configuration point at your aggregation layer and have port-extenders for floor switches seems really neat. It makes sense to bring a data-centre technology that works well out into the campus.

Curiously, they say this will work with 6500s! Which would be nice, but they don’t say what IOS you need to be running. I am a little pessimistic about these things, so I am guessing they need to run an IOS that hasn’t been released yet (ie, the marketing people jumped the gun). But that’s just me.

Definitely keen to get my hands on some of these.