VIRL versus Junosphere

I’ve been using Junosphere a lot recently, and it’s a great tool – quick and easy creation of topologies without the need to go to a physical lab to try things out. Takes the guesswork out of a lot of things, which is a real bonus. There are obviously a few things you can’t do in a virtual environment that would be possible in a real one (e.g. QoS, MTU greater than 2000 bytes, MS-MIC in an MX), but it caters for 80% of what you need.

I always thought that it put Juniper leagues ahead of Cisco because you can buy credits to use the system right on the front page. Cisco were late to the party with something called VIRL – Virtual Internet Routing Lab.  They were late, but rumour had it that a lot of developers moved from Juniper to Cisco to bring VIRL about.  However Junosphere always had the edge for the networking student (as we all remain, whether we are JNCIE or not) because of its accessibility – with VIRL you had to be a Cisco customer and gain access through your account manager.  I’ll stick with GNS3 thanks!

That appears to have changed now, and you can get access to VIRL ‘personal edition’ for $199 per year.  Now we’re talking.  Since it runs on Openstack, you can run up other third-party VMs alongside NXOS, IOS and IOS-XE.  Network Inferno has a nice guide on integrating Juniper’s vSRX (formerly Firefly) into VIRL, which looks pretty comprehensive, although I’ve not tried it yet.

I think need to get a copy of this – only problem is it needs me to get a new quad-core laptop with the virtualization extensions in the BIOS to replace my cranky old Lenovo.  Ho hum!

Multicast frustration.

Ugh!   Just been doing some testing with PIM sparse mode and run up against what is probably a code issue.

The situation – two routers connected together over ethernet.  R1 has ‘ip igmp join-group 230.0.0.1’ on its ethernet interface – this makes it a listener for that group.   R2 is a PIM bootstrap router (BSR) and rendezvous point (RP).   Now, I should be able to ping 230.0.0.1 from R2 and receive a response, but I wasn’t getting anything.

IP SLA-dependent static routing

Just for reference really: I needed to have a static route whose presence depended on the IP reachability of a host. If the host wasn’t there, the static route should disappear, and default routing take over.

Trunking and sub-interfaces on the same switchport

For some reason, I never knew that you could trunk and use a sub-interface on the same port of a Catalyst 6500, so I’m recording it here for personal reference.

What I wanted to achieve was to connect two 7600 routers over an Ethernet pseudowire (E-Line, EoMPLS circuit, AToM circuit, Martini circuit – whatever it’s called these days).   The reason I needed to do so was that the interveninig 6500 routers were only getting a default route via BGP from the 7600s.

Configuration lock in IOS

Just read a really nice guide to exclusive configuration mode access in IOS, written by Joe Harris.

Its a useful way of stopping other people pulling the rug from under your feet (while you’re busy scratching your head about some route-map or other).

Really simple policy-routing in IOS

For some reason (and for quite a long time) policy routing seemed a bit of a scary subject.  I’ve noticed other people don’t like it very much either, but it is actually not all that bad.

MTU setting differences between 7600 and ME3750

Just for personal reference really:

The ME3750 has several ways of setting the MTU:

L2TPv3 revision notes – architecture

L2TPv3 has been designed to transport layer-2 frames of various types over a layer-3 backbone.  Some aspects of the configuration are similar to that of EoMPLS – just without the need to deploy MPLS!

Packets are tunneled across the layer-3 network completely transparently, such that the two devices appear to be connected together. In the case of ethernet tunneling, there is no learning of MAC addresses – what goes in one side, comes out the other. That includes CDP, Spanning Tree and so on.

Cisco 3750 software recovery

A colleague of mine just called, having done an “erase flash” on a 3750. He did this because there was only 16MB of flash on the switch and therefore not enough room for two images at the same time. What he didn’t expect was that the switch would subsequently reboot and end up in bootloader mode with no software on it…

So here’s what we did. I thought I’d write this up because I found it a bit difficult locating the information on Cisco.com.

Loading IOS image via TFTP in ROMMON

Always a pain in the backside, isn’t it, when you’re stuck with a router that has no image on it. Even if you up the baud rate to 115,200 it still takes an age to download an image over the serial port to the thing.

More recent routers seem to have a TFTP client built-into the ROMMON software though. Not entirely sure how recent a router has to be in order to have this facility, but it’s very handy and saves a lot of time.

You basically set a few environment variables so that the router knows what its IP address is, where the server is and what the file it should download is. After that, just issue the “tftpdnld” command and off it goes. Here’s what you do:

rommon 11 > IP_ADDRESS=192.168.1.5
rommon 12 > IP_SUBNET_MASK=255.255.255.0
rommon 13 > DEFAULT_GATEWAY=192.168.1.1
rommon 14 > TFTP_SERVER=192.168.1.10
rommon 15 > TFTP_FILE=c1841-advipservicesk9-mz.124-13a.bin
rommon 16 > tftpdnld
.
IP_ADDRESS: 192.168.1.5
IP_SUBNET_MASK: 255.255.255.0
DEFAULT_GATEWAY: 192.168.1.1
TFTP_SERVER: 192.168.1.10
TFTP_FILE: c1841-advipservicesk9-mz.124-13a.bin
TFTP_MACADDR: 00:13:80:7b:20:1e
TFTP_VERBOSE: Progress
TFTP_RETRY_COUNT: 18
TFTP_TIMEOUT: 7200
TFTP_CHECKSUM: Yes
FE_PORT: 0
FE_SPEED_MODE: Auto Detect
.
Invoke this command for disaster recovery only.
WARNING: all existing data in all partitions on flash will be lost!
Do you wish to continue? y/n: [n]: y
...
Receiving c1841-advipservicesk9-mz.124-13a.bin from 192.168.1.10 !!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
....
File reception completed.
Validating checksum.
Copying file c1841-advipservicesk9-mz.124-13a.bin to flash.
program load complete, entry point: 0x8000f000, size: 0xc100
.
Initializing ATA monitor library.......
.
Format: Drive communication & 1st Sector Write OK...
Writing Monlib sectors.
................................................................................
..................
Monlib write complete
Format: All system sectors written. OK...
Format: Operation completed successfully.
Format of flash: complete
program load complete, entry point: 0x8000f000, size: 0xc100
Initializing ATA monitor library.......
rommon 17 >
Once that’s done, just issue a reset command and it should boot into IOS.