topic Re: CRC errors with 2 1300 bridges in Wireless

CRC errors with 2 1300 bridges

inlandkw — Sun, 04 Jul 2021 16:51:41 GMT

I have set up a couple Cisco 1300s to bridge out LAN between a couple buildings and am wondering something. We're getting decent 802.11G throughput (about 22mbps) but looking at the receiving end of a large file transfer, we are getting quite a few header CRC errors. We have both the access points on the roof and each has a 13.5dB Yagi attached to it. I've already checked the other wireless stuff we have here and it's on a different channel, and the 1300s are set to use the least congested channel. Would I be running into problems if the signal is bouncing back off the neighbouring building? After one big file transfer (about 1GB), and a weekend of sitting around unused, I'm up to:

CRC Errors 1246676

Header CRC Errors 2918492

Is that an acceptable amount?

Re: CRC errors with 2 1300 bridges

ndoshi — Wed, 04 Aug 2004 04:09:10 GMT

I think yes .

I would say CRC errors are normal . If you are getting ping drops and you are too much offset from theoratically calcualted throughput you should look into RF interference , concatenation , antenna alignment etc .

show dot association all

show int d0 stat

See if you are not getting too many rts and cts

retries .

Thanks

Re: CRC errors with 2 1300 bridges

inlandkw — Wed, 04 Aug 2004 16:43:47 GMT

As of now:

RTS retries: 22

CTS not received: 304

RTS Transmitted: 1238

Normal? Copying across the connection, we were getting about 200KB/sec (says its connected at 802.11G) What kind of actual throughput can you expect out of the 54mbps peak of 802.11G?

Re: CRC errors with 2 1300 bridges

skilambi — Wed, 01 Sep 2004 01:33:12 GMT

How did you measure your throughput to be 22Mbps, I have the exact same set up and I too have a lot of CRC errors which I don't think is anything to be concerned about.Also when you say 200Kb/sec I am a little confused since you also mentioned you got about 22Mbps throughput, could you clarify that?

Are there any inbuilt utilities in the 1310 that can measure signal strength from the other bridge?

Re: CRC errors with 2 1300 bridges

edwardsjj — Tue, 21 Feb 2006 22:46:21 GMT

inlandkw,

I have an Yagi mounting question. Next month I'm setting up a wireless bridge with 1310's and Yagi's at each end. My question is, which way do I turn the Yagi's? In other words, do the antenna's point at each other? Which direction does the signal travel? Thank you for any assistance.

Re: CRC errors with 2 1300 bridges

jcornford — Wed, 22 Feb 2006 18:31:09 GMT

If your link is associating at 22Mbps you ought to get more than 200KB/sec. Assuming a one way data test, you should get speeds at least 1000KB/sec. CRCs are normally due to noise or multipath (lots of metal sheeting can cause this like on industrial buildings), and all of this could degrade your link.

You say you've configured for the least congested channel. Did you do this after running a carrier test? Can you post your configs and the output of the following commands (do them on the bridge at your local end)?

dot11 dot11 0 carrier busy

show dot11 asso all

Also, I need to know roughly the distance between the antennas.

Re: CRC errors with 2 1300 bridges

jcornford — Wed, 22 Feb 2006 18:33:29 GMT

You point the round end of the yagis at each other. The other end fixes onto some u-bolts that go onto your mast. The signal is radiated out from the round end for the most part.