December 15, 2011

We spent a few hours last night and tonight working out the kinks with our new Cogent fiber to our new office, and boy is it zippy...we're clocking almost 90Mbps downstream and 75Mbps upstream, which we enjoy.

But along the way, we discovered one major (and many minor) issues that were causing intermittent connection loss. The thread below provides a more detailed description, but in short, the core routers at Cogent have auto-negotiation for port speed & duplex settings disabled, causing our Cisco UC routers to fail back to 100Mbps half-duplex. This begins to introduce massive amounts of collisions on the link, causing the device to force thousands of connection resets, which initially just slows down the link dramatically, and eventually causes the Cisco gear to barf entirely. Thanks to some help from friends at Cisco, Cogent, and our own investigation, we finally narrowed it down to this...fixed the port to 100Mbps, full duplex and we're good to go.

# configure terminal
# interface GigabitEthernet 0/0
# speed 100
# duplex full
# exit
# exit
# copy running-config startup-config

http://www.mail-archive.com/leaf-user@lists.sourceforge.net/msg08735.html

Moving forward we're also looking at adding a Peplink or similiar multi-WAN router to distribute traffic across multiple channels (primarily for redundancy)...anyone have any experience with them?



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