Michael McNamara

technology, networking, virtualization and IP telephony

Wake On LAN and Directed Broadcast

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I’m not sure the majority of engineers realize that both Nortel and Cisco have directed broadcast disabled by default these days.

I recently came across a problem where I needed to remotely start a PC that supported Wake On LAN. Since I do most of my development on Linux I downloaded a Wake On LAN perl script from José Pedro Oliveira.

Wake On LAN works by sending specially crafted UDP packets to the MAC address of the PC. If the workstation sending the UDP packet is on the same VLAN or Layer 2 network this really isn’t a problem. If the workstation sending the UDP packets is on a different VLAN or Layer 2/3 network we need to rely on the router to send a broadcast to all devices in the target VLAN or Layer 2/3 network.

In Device Manager you’ll find the option under the VLAN -> IP,

nortel8600-directedbroadcast1

Within the CLI you’ll need to issue the following command;

ERS8600:5# config vlan 2 ip directed-broadcast enable

Cheers!

ADAC and VLAN Configurations (Part 2)

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In a previous post titled ADAC and VLAN Configurations I described some issues we were having with some of our switches where VLAN memberships were mysteriously changing. We suspected ADAC and we were right on with our suspicions.

We performed some exhaustive testing with ADAC over the past few weeks and can confirm, as Roberto alluded too, that ADAC will dynamically reconfigure any switch port that has ADAC enabled to the VLAN membership and PVID setting that was set when ADAC was first enabled on the switch port. In our tests we configured an edge port as a member of VLAN 10 and then enabled ADAC on that port. We then added the edge port to VLAN 11, removing it from VLAN 10. When the port went into an oper-down state ADAC added the edge port back to VLAN 10 and removed it from VLAN 11. We confirmed the same behavior with respect to the PVID changing.

In short if you need to make a VLAN membership or PVID change to an ADAC enabled port you MUST disable ADAC on the port before making the change and then re-enable ADAC when you have completed your change. As a side note any Nortel IP phone that is connected to the port will most likely timeout and reboot itself when you disable ADAC.

While I don’t necessarily disagree with the behavior it would be nice for either the CLI of Device Manager to alert someone if they tried to change the VLAN membership of a port that had ADAC enabled. (hint hint Nortel)

Cheers!

Virtual Routing Redundancy Protocol (VRRP)

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What is Virtual Routing Redundancy Protocol? In short VRRP is a standards based protocol that provides redundant default gateways when multiple routers/switches are connected to the same Layer 2 network. A virtual IP address is shared between one or more routers/switches providing redundancy against a router/switch failure.

We’ve been using VRRP in conjunction with SMLT to make sure that either core ERS 8600 switch in a cluster could assume the default gateway for any specific VLAN should the other switch fail. While I’m not at liberty to get into specifics I can tell you that we recently ran straight into a wall with our VRRP configuration. We had about 60+ VLANs (port based) on an ERS 8600 switch cluster where the VRRP ID for each VLAN was set to “1”. While Nortel had previously said this configuration was supported, we ran into significant issues testing some new software code for the 8600.

128px-nuvola_apps_importantsvgIn short Nortel is now advising that you MUST have unique VRRP IDs. Nortel recommends as best practice that you use the VLAN ID but that can be problematic since valid values for the VLAN ID are between 1..4096 and valid values for the VRRP ID are between 1..512. In my case the VLAN IDs were between 1 and 200 so I was able to match them up.

config vlan <VLAN ID> ip vrrp <VRRP ID> address <IP ADDRESS>
config vlan <VLAN ID> ip vrrp <VRRP ID> backup-master enable
config vlan <VLAN ID> ip vrrp <VRRP ID> enable

ERS8600:5# config vlan 1 ip vrrp 1 address 10.10.1.1
ERS8600:5# config vlan 1 ip vrrp 1 backup-master enable
ERS8600:5# config vlan 1 ip vrrp 1 enable
ERS8600:5# config vlan 2 ip vrrp 2 address 10.10.2.1
ERS8600:5# config vlan 2 ip vrrp 2 backup-master enable
ERS8600:5# config vlan 2 ip vrrp 2 enable
ERS8600:5# config vlan 9 ip vrrp 9 address 10.10.9.1
ERS8600:5# config vlan 9 ip vrrp 9 backup-master enable
ERS8600:5# config vlan 9 ip vrrp 9 enable

I believe Nortel is now recommending RSMLT in place of VRRP which we’ll be using going forward. If you’ve been using a VRRP ID of 1 in every VLAN you might want to consider changing your configuration. I hope to write a post about RSMLT in the near future detailing how to configure it and the advantages using RSMLT over VRRP.

A personal note of Thanks to Richard M. and Roger G. from Nortel for their help and assistance in troubleshooting this problem.

Cheers!

HP NIC Teaming with Nortel Switches

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hpweb_logo I recently needed to look at HP’s NIC Teaming feature within their Proliant server product line to provide “ultra” high-availability to a new Windows 2008 Cluster which was running Microsoft Exchange 2007. It seems that NIC teaming has come a long ways from the original NIC fault tolerance where one NIC would simply act as a standby should the first loose LINK with the network switch.

HP’s NIC Teaming now supports 802.3ad (LACP) which provides a load balanced and fault tolerant solution. I’ve posted several documents to my website for anyone that might be looking for additional information.

Here is a very good document that outlines NIC teaming from head to toe, along with additional documents that outline the different capabilities and what operating systems are supported.

In short you need to setup an LACP group on the Nortel switch for any ports that you want to be in the LAG (Link Aggregation Group). You can leave the HP NIC teaming options set to Automatic and it should negotiate as a “802.3ad Dynamic with Fault Tolerance” when you have the Nortel switch configuration properly.

5520-48T-PWR> enable
5520-48T-PWR# config term
5520-48T-PWR(config)# interface FastEthernet 1/1-2
5520-48T-PWR(config-if)#lacp aggregation port 1/1-2 enable
5520-48T-PWR(config-if)#lacp mode port 1/1-2 active
5520-48T-PWR(config-if)#lacp key port 1/1-2 101

Cheers!

Reload command on Nortel Switches

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In today’s demanding business environments a lot of changes need to be made remotely and sometimes even the best laid plans go south. Thankfully Nortel offers the “reload” command in their Ethernet Switch and Ethernet Routing Switch series. I don’t believe the command is available for the 1600 or 8600 series. For those folks that are familiar with Cisco routers this command is identical although the syntax is different. If your making changes that could hang the switch or otherwise leave it improperly configured the reload command will automatically restart the switch after a specified interval has passed. If your configuration changes are successful you can cancel the reload command. If you somehow get disconnected from the switch you only need to wait until the switch reloads the original configuration.

ERS5520-PWR#reload ?
cancel           Cancel a previous scheduled reload
force            Do not ask for confirmation
minutes-to-wait  Minutes to wait before reboot
<cr>

Cheers!

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