We have strange DHCP issue with Polycom-VVX Lync phones using C2900 DHCP server.
DHCP configuration works with Cisco 2800 router, but same dhcp configuration doesn't work with C2900 router.
Only difference, Cisco 2800 router accepts option 43 without "EXT" word. But in C2900, we need to add option ext 43 hex
See below the voice vlan dhcp pool for C2900
ip dhcp pool MQT-L8-Lync-Phones
network 172.22.12.0 255.255.255.0
next-server 10.82.20.50
default-router 172.22.12.1
dns-server 10.82.10.250 10.18.15.39
option 42 ip 10.82.10.250
domain-name govnet.nsw.gov.au
option 160 ascii ftp://ausvwlyncmed01.nswgov.ucfx.com
option ext 43 hex 010c.4d53.2d55.432d.436c.6965.6e74.0205.6874.7470.7303.1a6c.796e.6370.6f6f.6c30.312e.6e73.7767.6f76.2e75.6366.782e.636f.6d04.0334.3433.0525.2f43.6572.7450.726f.762f.4365.7274.5072.6f76.6973.696f.6e69
option ext 43 hex 6e67.5365.7276.6963.652e.7376.63
