guys plugging a BH into a CISCO getting high number of CRC errors… changed cable, ends, ends, cables, middles, BH, ports on switch…
question: could a poor link (RF) cause CRC errors, i.e could a packet become corrupted on the RF part and then pass through to be detected on the Switch.
question: on the CMM are the FCS errors equiv to CRC errors, we are seeing high number of these FCS errors on the CMM ports that have BH plugged into them… AP’s are fine…
question: could a poor link (RF) cause CRC errors, i.e could a packet become corrupted on the RF part and then pass through to be detected on the Switch.
Good question. My thoughts would be no. I would think that Canopy has implemented some type of mechanism which does error detection, correction via re-transmission on its air interface. If it detects a packet was corrupted in RF transit, I would think it requests a resend, like TCP. I would assume that the packet would not be converted and passed to the Ethernet interface until the packet was good. But, I could be wrong.
Have you tried fooling with the Link Negotiation Speeds on both the BH and Cisco Interface? How long is your cable?
question: on the CMM are the FCS errors equiv to CRC errors, we are seeing high number of these FCS errors on the CMM ports that have BH plugged into them.... AP's are fine....
I have seen this also but unfortunately I don't have the answer. As I stated in an earlier post, we had some issues with BHs and the Outdoor Rated, Shielded Cable from Best-Tronics. There were tears in the jacket and inner-shielding. Water got inside the cable and caused all types of errors.
So are you saying that you see an identical number of FCS errors on a particular CMM port as CRC errors on the BH that terminates into that port?
Do any of these BH's have surge suppressors on them between the cable and CMM?
I too have seen this… forcing duplex resolved the issue for me (100 - half worked best for me).
Have you tried fooling with the Link Negotiation Speeds on both the BH and Cisco Interface? How long is your cable?
I usually get issue if I try forcing the CISCO to a setting. Cable is about 70ft.
So are you saying that you see an identical number of FCS errors on a particular CMM port as CRC errors on the BH that terminates into that port?
can't be sure as been swapping ports need to reboot CMM and clear counters at the same time
Do any of these BH's have surge suppressors on them between the cable and CMM?
nop....
I think I will end up ordering pre-made cables.
Cisco Switch or Router?
If connecting directly to a router, you need to put a managed switch in between to set port speeds correctly.
Cisco switch 3550, we do some layer 2/3 stuff on it.
why can’t you go direct to a router, can you not set speeds on a router
We had CRC issues when we upgraded to a 3600 without a fast ethernet card.
Internet --> ISP Switch --> airCloud 3600 Router --> 2924 Catalyst --> BH20
Once we added the fast ethernet switch and set everything to 100/full everything cleared up.
well I have a 3550 switch… so that should be ok…
I know CISCO kit is bad at negotiating/talking with other non-cisco kit.
We have now plugged the BH into a CMM and then CMM into switch, seems ok, but there could be a problem between CMM and BH and we will never see it…
vj wrote: question: could a poor link (RF) cause CRC errors, i.e could a packet become corrupted on the RF part and then pass through to be detected on the Switch.
No a poor RF link cannot cause CRC errors on the Ethernet interface. The cyclic redundancy check is done between the two physical interfaces that are directly connected, i.e. the Canopy Ethernet port and the Cisco Ethernet port.
Keep in mind that Canopy will NOT pass bad packets. We will retransmit until they are correct so if its good data coming in then its good data going out.
CRC errors on the Ethernet mean one of two things, either you have a physical issue (cable, cisco port, Canopy port) or your cable is ran next to something putting too much noise on the line.
I would try forcing to 10/full as the first step.
thanks…
I didn’t think that an error on the RF side would get passed through. I have checked and replaced everything, with about 5Mbits of traffic passing through the BH, it runs up CRC errors at the rate of 4/5 per second. Port keeps going orange.
As explained earlier I have for the time being put the BH into the CMM and connected the CMM to the switch. I will try out your suggestion of forcing the port to 10/full, but my experience with CISCO in the past has been that it doesn’t like being told what to do.
In terms of something causing noise, we have 4 other cable running in the same line and they seem ok. The CMM is powered by DC power running in conduit 2.5 ft away so I can’t think of any EMF type of noise. I am waiting for a cable certifier to test the cables and the ethernet ports.
Fluke sells a cable tester for about $130 US which tests the 4 pair plus the drain wire connectivity.
Fluke MT-8200-49A MicroMapper
I need to get a full certifier for a structured cabling job for a new hotel, so I am planning to the get the DTX series, will do fiber too ($6000).
The MT-8200 looks like a nice piece of kit, I might get one to test and see if the installtion guys can make use of it, at customer site. Thanks.
FCS errors:
In the CMM all my BH are showing high number of FCS errors, 1-6million. All my AP’s are showing 0 or on the off case 1.
Below are 3 definitions for Alignment, FCS and CRC errors.
Alignment Errors:
An Alignment Error indicates a received frame in which both are true:
The number of bits received is an uneven byte count (that is, not an integral multiple of 8)
The frame has a Frame Check Sequence (FCS) error.
Alignment Errors often result from MAC layer packet formation problems, cabling problems that cause corrupted or lost data, and packets that pass through more than two cascaded multiport transceivers. See “FCS Errors” for more information about interpreting Alignment Errors.
FCS Errors
Frame Check Sequence (FCS) Errors, a type of CRC, indicate that frames received by an interface are an integral number of octets long but do not pass the FCS check. The FCS is a mathematical way to ensure that all the frame’s bits are correct without having the system examine each bit and compare it to the original. Packets with Alignment Errors also generate FCS Errors.
Both Alignment Errors and FCS Errors can be caused by equipment powering up or down or by interference (noise) on unshielded twisted-pair (10BASE-T) segments. In a network that complies with the Ethernet standard, FCS or Alignment Errors indicate bit errors during a transmission or reception. A very low rate is acceptable. Although Ethernet allows a 1 in 108 bit error rate, typical Ethernet performance is 1 in 1012 or better
CRC Errors
A Cyclic Redundancy Check (CRC) Error is an RMON statistic that combines “FCS Errors” and “Alignment Errors”. These errors indicate that packets were received with:
A bad FCS and an integral number of octets (FCS Errors)
A bad FCS and a non-integral number of octets (Alignment Errors)
CRC Errors can cause an end station to freeze. If a large number of CRC Errors are attributed to a single station on the network, replace the station’s network interface board. Typically, a CRC Error rate of more than 1 percent of network traffic is considered excessive.
In my case it could me that the CRC errors are due to FCS errors as I am not seeing Alignment errors.
Our cables are shielded, does not affect AP’s, and kit is not be powere up and down. I will continue my investigations, but if anyone can help/advice I would greatly appreciate it.
I tried all of the following
Putting unmanaged switch in between
Changing the PoE
Changing the Speed settings and card to Fast ethernet
but finally that solved my problem was changing the cable from UTP to STP
You never know how imp small things can be at times