Subscriber called me today saying she was having great problems getting on the internet.
Configuration is a 911G-2HPnD on the roof, supplying NAT and DHCP, and a hAP indoors, configured as a brainless home WiFi AP with all interfaces bridged together.
Had the devil’s own time logging into the hAP remotely, kept disconnecting. Got lots of timeouts on pings from the 911G to all devices inside the house. Finally saw that “Rx Length Error” on 911G’s ethernet was steadily incrementing. Searched for the meaning of this metric with no success.
Had her unplug all indoor devices from the hAP to see if one of them was hosing the connection, but there was no change. Then had her move the 911G’s cable from the first port to the last port on the hAP, and the problem disappeared.
Examined the ports on the hAP. The only configuration difference was that port 0 had l2mtu=1600 while all the others had l2mtu=1598. (These must be defaults, because I don’t set mtu values). I set the l2mtu on port 0 to 1598 and had her retry it to see if that would fix the problem, but Rx length error immediately started incrementing again, so I had her put it back in the working port so she could get her work done.
Port 0 on a hAP is “special” because it doesn’t communicate with the switch chip, so it had to be placed in a software bridge. I’ve checked the bridge values for MTU funnies, but don’t see any.
Have I done something stupid in the bridging configuration to cause this, or should I RMA this hAP for a bad port? One more data point: her connection seemed to be running fine when I replaced her dead ASUS WiFi AP with the hAP two days ago.
Here is the ethernet configuration on the hAP (after I changed the l2mtu on port 0):
0 S name="ether1" default-name="ether1" mtu=1500 l2mtu=1598 mac-address=D4:CA:6D:6D:2F:C6
orig-mac-address=D4:CA:6D:6D:2F:C6 arp=enabled auto-negotiation=yes
advertise=10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full full-duplex=yes
tx-flow-control=off rx-flow-control=off speed=100Mbps master-port=none
bandwidth=unlimited/unlimited
1 RS name="ether2" default-name="ether2" mtu=1500 l2mtu=1598 mac-address=D4:CA:6D:6D:2F:C7
orig-mac-address=D4:CA:6D:6D:2F:C7 arp=enabled auto-negotiation=yes
advertise=10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full full-duplex=yes
tx-flow-control=off rx-flow-control=off speed=100Mbps master-port=none
bandwidth=unlimited/unlimited switch=switch1
2 S name="ether3" default-name="ether3" mtu=1500 l2mtu=1598 mac-address=D4:CA:6D:6D:2F:C8
orig-mac-address=D4:CA:6D:6D:2F:C8 arp=enabled auto-negotiation=yes
advertise=10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full full-duplex=yes
tx-flow-control=off rx-flow-control=off speed=100Mbps master-port=ether2
bandwidth=unlimited/unlimited switch=switch1
3 RS name="ether4" default-name="ether4" mtu=1500 l2mtu=1598 mac-address=D4:CA:6D:6D:2F:C9
orig-mac-address=D4:CA:6D:6D:2F:C9 arp=enabled auto-negotiation=yes
advertise=10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full full-duplex=yes
tx-flow-control=off rx-flow-control=off speed=100Mbps master-port=ether2
bandwidth=unlimited/unlimited switch=switch1
4 RS name="ether5" default-name="ether5" mtu=1500 l2mtu=1598 mac-address=D4:CA:6D:6D:2F:CA
orig-mac-address=D4:CA:6D:6D:2F:CA arp=enabled auto-negotiation=yes
advertise=10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full full-duplex=yes
tx-flow-control=off rx-flow-control=off speed=100Mbps master-port=ether2
bandwidth=unlimited/unlimited switch=switch1
Here is the ethernet configuration on the 911G:
0 RS name="ether" default-name="ether1" mtu=1500 l2mtu=1600
mac-address=D4:CA:6D:84:E8:E5 orig-mac-address=D4:CA:6D:84:E8:E5
arp=enabled auto-negotiation=yes
advertise=10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full
full-duplex=yes tx-flow-control=off rx-flow-control=off speed=100Mbps
master-port=none bandwidth=unlimited/unlimited
Here is the bridge configuration:
0 R name="AP-BRIDGE" mtu=1598 actual-mtu=1500 l2mtu=1598 arp=enabled mac-address=D4:CA:6D:6D:2F:C7
protocol-mode=rstp priority=0x8000 auto-mac=yes admin-mac=00:00:00:00:00:00
max-message-age=20s forward-delay=15s transmit-hold-count=6 ageing-time=5m
Bridge ports:
0 I interface=ether1 bridge=AP-BRIDGE priority=0x80 path-cost=10 edge=auto point-to-point=auto
external-fdb=auto horizon=none auto-isolate=no
1 interface=AP bridge=AP-BRIDGE priority=0x80 path-cost=10 edge=auto point-to-point=auto
external-fdb=auto horizon=none auto-isolate=no
2 interface=ether2 bridge=AP-BRIDGE priority=0x80 path-cost=10 edge=auto point-to-point=auto
external-fdb=auto horizon=none auto-isolate=no