Catalyst 3750 and jumbo frames

We're looking to implement a gigabit segment with a 3750 switch, with the latest apple imac G5 clients connected and and an xserve G5 connected doing link aggregation using a 4 port smalltree NIC.
Although the Xserve supports jumbo frames i believe the imac NICs DON'T support jumbo frames although the operating system does( the imac NICs DO support 1000T ) Ideally we'd want the 3750 switch to be configured for Jumbo frames. The 3750 switch we've chosen has all ports of 10/100/1000T with the SMI, so all ports will have the MTU set at 9000 if we enable jumbo.
Although the Xserve will be fine, i'm worried about traffic that ingresses from the xserve and egresses out to a 10/100/1000 port to which an imac is connected which i believe does not support Jumbo frames. What are the issues in terms of connectivity and dropped packets for an imac G5 connected to a 3750 ?
seeing as the MTU is set globally and all our ports are gigabit, and machines will be connected to these ports that don't support jumbo but are advertised as having 'gigabit capability'
Sorry if these sounds like an incoherent rant, but i needed to provide as much info as possible. Help much appreciated

just to add, in comparison HP gigabit switches can do jumbo vlan on a per vlan and per port basis it's a shame the 3750 can't do that

Similar Messages

Interconnecting Catalyst 3750 and 2948G-L3

I am trying to interconnect a Catalyst 3750 and a 2948G-L3 using fiber GBIC. The interfaces where the GBIC and fiber are attached show up as physically down. I have tried different ports and also changed both switches. No Luck. If I connect a 3524 to the 3750 using the same connection it works.
Are 2948G-L3 switches compatible with the 3750?
Thanks,
VT

Should have no problem. Can you try the following on the 3750's gig interface:
speed nonegotiate
See of the link comes up.
Please rate all posts.

FTTH connection proper MTU Size and Jumbo frames

I've recently moved to a ISP that provides a 4mbps connection through FTTH(Single OFC). There is a EPON ONU in my premise from which a RJ-45 lan cable is connected to my Intel DH67CL1 board based PC. manual says, the NIC is a gigabit ethernet card. I tried setting MTU of 8996 and I can ping and browse fine. But, I'm totally in dark whether this value is optimum and works flawlessly browsing sites. How to find and set the proper MTU for a fibre network like this? Is the value correct?
I tried like this decreasing mtu value:
ifconfig eth0 mtu 8997
SIOCSIFMTU: Invalid argument
then,
ifconfig eth0 mtu 8996
^^^ No error message and it seems accepting.
BTW, from arch wiki, I saw that the driver module(e1000e which is used here) used by NIC have some bug report filed wr.to Jumbo frame. Am I doing things correctly? Earlier MTU was at default 1500. Please guide. thank you
Some drivers will prevent lower C-states
Some kernel drivers, like e1000e will prevent the CPU from entering C-states under C3 with non-standard MTU sizes by design. See bugzilla #77361 for comments by the developers.
https://wiki.archlinux.org/index.php/Ju … mbo_frames

yeah, i actually talked to support and they told me the same thing. just another example of misleading information from Linksys as here is what the manual and the help page say:
MTU
MTU is the Maximum Transmission Unit. It specifics the largest packet size permitted for Internet transmission. Select Manual if you want to manually enter the largest packet size that will be transmitted. The recommended size, entered in the Size field, is 1500. You should leave this value in the 1200 to 1500 range. To have the Router select the best MTU for your Internet connection, keep the default setting, Auto.
no where in that description does it say that 1500 is the maxmium.
because this is also a gigabit switch, one would expect that jumbo frame support is not out of the realm of possibility. as a point of reference any other $50 (or less) gigabit switch supports this, but that's what i get for expecting too much from Linksys.
thanks for the info.

Linksys SE2800 and jumbo frames

Does the Linksys SE2800 gigabit 8 port switch support jumbo frames? Anyone have this switch? Any issues? Looking to replace a netgear gigabit switch that likes to forget that it has gigabit machines connected to it.

Hi Michael,
Actually had a chat with a colleague at linksys regarding your question, but he referred me to a datasheet, which left me with the question I started with. The technician said yes it suppported Jumbo frames but he could post me nothing in black and white..
Why not look at the Cisco Small Business umnanaged product the SG100D-08. It offers as the datasheet suggets;
Peace of mind:
All Cisco 100 Series switches are protected for the life of the product by the Cisco Limited Lifetime Hardware Warranty
Also, even though an unmanaged product, this series supports such features as;
1. Green Energy—Efficient Technology
The Cisco SG 100D-08 switch supports Green Energy-efficient
Technology. It can enter sleep mode, turn off unused ports, and adjust
power as needed. This increases energy efficiency to help businesses use
less power and save money.
2. Jumbo Frame Support
The Cisco SG 100D-08 switch supports frames up to 9,000 bytes called
jumbo frames. Jumbo Frame support improves network throughput and
reduces CPU utilization during large file transfers, such as multimedia files,
by allowing larger payloads in each packet.
regards Dave

SRW2048 and Jumbo frames

I have a Cisco SRW2048 (Firmware 1.2.2d, boot 1.0.0.05) on which I have enabled jumbo frames but yet when I attempt with a Windows 2003 server to ping the mgmt IP of this switch with a frame over 1472 (ping -f -l 1472 w.x.y.z) I get a response of "Packet needs to be fragmented". The server is connected to a Netgear gig switch (GS724AT) that has jumbo frames enabled and working as I can talk to other devices using jumbo frames. Attempts to access the SRW2048 switch fail on packets larger than 1472. I have also attempted a Windows 7 box using jumbo frames to no success. The Windows 7 box works when connected to the Netgear switch but when I move the connection back to the SRW2048, jumbo frames on the windows box stop working.
Any help or suggestions would be appreciated.
Thanks.
David

On the SF-300 and SG-300 for Jumbo to work the Enable Jumbo checkbox must be unchecked. Either I don't understand Cisco logic or it's a bug in the GUI.

Dual nic NAS and Jumbo Frame

I am posting this on the server area because I doubt I am going to get an answer anywhere else.
I have a linux based NAS running netatalk and avahi (afp server and bonjour) with two nics and I have a brand new Mac Pro with two NICS. What I want to do is run a crossover cable between the NAS and the Mac Pro in addition to both being plugged into the normal network. The normal network would have 1500 byte mtu so my internet performance and all of the various vintages of print servers work ok. The dedicated network would have jumbo frames. As we get more Mac Pros, we would add a switch and more machines to this secondary jumbo frame network.
That in theory should work fine (I have done it with other operating systems). My quandary is how to get the Mac to always connect to the NAS via the Jumbo nic and not through the other nic? The Mac learns of the server via Bonjour, so how do I tell it to prefer the "appearance" of the server on the jumbo NIC vs the appearance on the normal network. I know with WINS or DNS I can override the name resolution with a LMHOSTS or hosts file entry, can I do the same with Bonjour?
Thanks for any help or any pointers in the right direction!

I think you are misguided in your assumption that I am not intimately familiar with TCP and don't know what I am talking about.
TCP does not "negotiate" MSS, it advertises the MSS of each side to the remote in the 3 way handshake. It is perfectly acceptable to have asymetric MSS values. TCP does NOT NEGOTIATE a common MSS size. On a LAN, this will result in a functional communication. UDP however does not have such mechanisms and will fail.
TCP will also not function properly in the scnario of my local workstaion with jumbos enabled communicating with a distant endpoint that also has jumbos enabled across a transit network that does not support the maximum MSS used by one of the end stations. For giggles let's say the far end is FDDI and has 4k frame size. Our transit does not support frame sizes larger than the "natural" frame size of 576 bytes. We will use a 4k frame size from me to the remote and a 9k from the remote to me. If the remote sends to me it can use the full 4k MSS of token ring because its less than my MSS. In the reverse my workstation would send 4k frames back to the token ring station. Successful communication would then depend on path MTU and intermediary routers to send ICMP type 3 code 4 messages to signal back to our end stations to reduce our MSS (assuming the DF bit is set on our traffic or the transit router is incapable of fragmentation).
This is perhaps a bit of a flippant example in that nobody would be running FDDI or Token ring anymore, but random entities on the internet will run jumbo frame and perhaps some other l2 technology we aren't familiar with.
Did you ever deal with someone on a token ring segment trying to hit 3Com's web site when it was fddi or token ring? I have on several occasions. I also see this with VPNs all the time. Cisco's genius recomendation is to reduce your MSS on your server as some of their products don't support PMTU. I have had a Cisco <-> Juniper VPN where transfers worked one way because the Juniper would silently strip the DF bit from the packet and fragment it and the Cisco router (38xx) wouldn't do the same in the reverse direction. I also went through **** with the Nortel Contivity VPN devices while they sorted out what to do with the whole MTU negotiation issue.
I have spent many hours of my life pouring through sniffer captures because of mismatched MTUs. Let's not forget the old days of FDDI backbones with ethernet segments bridged across them and FDDI attached servers... mismatched buffers... no thanks.
I therefore don't want to waste my time troubleshooting some bizzare networking issue when there is a perfectly valid way of solving the issue for absolutely minimal expense. I am moving large files here (certainly large enough to get well out of TCP slow start), we easily saturate the full gig link minutes at a time and a saturated gigabit link at standard frame size is inefficient due to the interpacket gap which is locked at 96 bit times for ethernet and the 40 bytes of TCP/IP header plus whatever application payload is prepended per packet on each link. Cutting the number of TCP/IP headers and (probably more importantly since most decent nics do checksum offload these days) application layer headers also reduces load on both client and server.
On large sequential bulk data transfers jumbo frame effectively increases performance and reduces overhead. Period. I have implemented it from the early days of Alteon hardware in Sun servers through Juniper EX products last week. Every iSCSI implementation I run into is jumbo frame based for those exact reasons.
That being said, I don't need to restrict anything. All I want to do is to override bonjour/mDNS for this particular host such that the Pro always communicates over the jumbo segment. This is easily accomplished in windows with an LMHOST entry or in a unix environment with a HOSTS file entry. Is there some way to override bonjour from the client side? I'm ok even statically defining the services presented by bonjour on this host.
I am also willing to force all bonjour requests through a DNS server, however Apple doesn't have any decent documentation on how this is accomplished in an enterprise environment.

Catalyst 3750 and VRRP

Can you tell me if your Catalyst 3750 switch (*not* the –E or –X variants) support VRRP ipv4? If so what version of firmware do I need?
Thanks - Walt

Walt
Support for VRRP was added in version 12.2(58)SE.
See this link for details -
http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-3750-series-switches/product_bulletin_c25-658743.html
Jon

Disable Multicast MAC Addr restricted in Catalyst 3750 and C3560G

Hi All,
I'm using Cisco 3750 Catalyst and C3560G, recent days ago i purchased a pair of WatchGuard Firewalls and put in the system to run HA Active/Active model.
The requirement to run WatchGuard Firewall HA A/A model is to allow ARP request if the response contains a multicast MAC Address in Routers and Switches.
I read somewhere that Routers and layer 3 switches, the default behavior is to follow RFC 1812, which says that the routers must not believe any ARP reply that claims that the link later address of another host or router is a broadcast or multicast address.
Can you pl show me the command to Allow all Multicast MAC Address for interfaces? Or disable RFC 1812 in order to get WatchGuard Firewall works properly.
Here is the information from WatchGuard firewall: "When you configure WatchGuard FireCluster in an active/active configuration, the cluster uses multicast MAC addresses for all interfaces that send network traffic. Before you enable FireCluster, make sure your network switches, routers, and other devices are configured to route network traffic with multicast MAC addresses.
Pl help. Thanks.

Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
My experience on 3750 has been generally only a reload will clear the detailed MLS QoS stats.
However, I thought could could clear the interface stats, although, if not, might be a bug in your IOS version (you didn't note actual 3750 model or specific IOS version being used).
Lastly, the interface stats don't clear at all? Reason I ask, disabling QoS doesn't preclude you still getting drops.

Catalyst 3750 and ACL

Hello. We have the next Settings in our SW. We crate an ACL and aplied to a SVI for Incomming Traffic, I understand that is not necesasry to allow the returning traffic in ACL, but we can't access to rdp for example when we add the ACL, if we remove it, the acces is ok, buet when we add again the access is deny, even we have a log entry, and the ACL i just for Incomming traffic. There is no another ACL. What should we check? What are we missing here?
Please see attached file
Thanks in Advance
interface Vlan64
ip address 10.147.64.254 255.255.255.0
ip access-group 134 in
access-list 134 permit udp any any eq bootpc log
access-list 134 permit udp any any eq bootps log
access-list 134 permit ip any 172.30.146.0 0.0.0.255
access-list 134 permit ip any 172.23.146.0 0.0.0.255
access-list 134 permit ip any 10.146.137.0 0.0.0.63
access-list 134 permit ip any 10.146.137.128 0.0.0.63
access-list 134 permit ip any host 10.146.81.240 log
access-list 134 permit ip any host 10.146.46.250
access-list 134 permit ip any host 10.146.46.157
access-list 134 permit ip 10.147.64.0 0.0.0.255 host 10.146.46.228
access-list 134 permit ip 10.147.64.0 0.0.0.255 host 10.146.137.99
access-list 134 deny   ip any 192.168.0.0 0.0.255.255
access-list 134 permit tcp any host 172.27.72.27 eq www
access-list 134 deny   ip any 172.16.0.0 0.15.255.255
“The next entry generates a log when I try RDP from 10.146.40.29 to 10.147.64.39”
access-list 134 deny   ip any 10.0.0.0 0.255.255.255 log
access-list 134 deny   ip any host 98.139.60.248 log
access-list 134 permit ip any any
access-list 134 permit icmp any any
"This is the log showed"
25w6d: %SEC-6-IPACCESSLOGP: list 134 denied tcp 10.147.64.38(3389) -> 10.146.40.
29(1150), 1 packet

What you are missing is a statement in the access list to permit traffic to the subnet of 10.146.40.0. Since there is no statement to permits this traffic then the line access-list 134 deny   ip any 10.0.0.0 0.255.255.255 log denies the traffic as it should.
To fix this problem you need to add a statement in the access list before that line to permit the traffic. The line might look something like this:
access-list 134 permit ip any 10.146.40.0 0.0.0.255
HTH
Rick

TCP Segmentation Offload and Jumbo Frames.

I have VmWare-OpenSolaris and VMXNET3 network card.
Can i enable subj?
#:> ifconfig vmxnet3s mtu 5000
ifconfig: setifmtu: SIOCSLIFMTU: vmxnet3s0: Invalid argument

Hi sdavids5670
Did you ever find a proper fix to your issue? was updating the N1Kv a solution?
I have exactly the same symptoms with a N1Kv [4.2(1)SV2(1.1a)], F5 (ASM), vmxnet3 guests, however I'm failing all RDP (win2k8r2) and SSH large packets (redhat); the rest of my traffic appears fine. This only occurs when the F5 resides on the same VEM or VMware host as you have seen. My packet captures are similar.
My work around is two fold. Firstly create rules to isolate the F5 onto hosts where guests are not utilising it and secondly, disable TCP offloading (I use IPv4 only). Neither of these are solutions.
I have not tried a non-F5 trunk (ie, perhaps a CSR1000v) to replicate this without the F5.
I suspected that the onbox / offbox issue was something specific about the logic of the VEM installed on the host (that's how I justified it to myself) rather than VEM->VEM traffic. It appears that only vEth -> vEth traffic on the same VEM is the issue. Also, I can only replicate this when one of the vEth ports is a trunk. I have yet to be able to replicate this if both are access port-groups (vEths).
I have yet to log a TAC as I wanted to perform testing to exclude the F5.
Thought that I would just ask....
Cheers
David

Fast EtherChannel between Catalyst 3750 and 2821 Router

Hi Guys
I'm trying to setup a Fast EtherChannel between a cat3750-smi and a 2821 router that consists of only 2 links.
I am following instructions per TAC, but I'm getting an error along the way;
On the cat3750:
interface port-channel 1
no switchport
Command Rejected: Not a convertable port
Can anyone help???
Also... do the IP Addresses for the EtherChannel need to be the same for both port-channels? Or do I assign the switch like 192.168.1.1 and the router 192.168.1.2 ?
Thanks!
Adam

Hi Adam,
The ip address cannot be same but it should belong to same subnet. So one side 192.168.1.1 and other side 192.168.1.2 will work fine.
Its better to convert your layer 2 port as a layer port fist so what you do the port which you want to be port channel go that that interface and convert with "switchport" command
once it is a layer 3 port configure with channel group and automatically layer 3 port channel will be created and you can sssign an ip address then.
Just give a try and update if it works.
Regards,
Ankur

Jumbo Frame support

Hi all
I have a vendor that wants to run an application called mirrorview to do a bandwidth test for a new application; the only requirement is that I support jumbo frames on my uplinks. I do not currently have my ports configured to support jumbo frames, are there any benefits or drawbacks to supporting jumbo frames? If so please post so I can weigh those options before I reconfigure my uplinks.
TIA Rodney.
FYI I am running 6500 hybrid in the core , and 3550-xx at the edge.

If jumbo frames are enabled only on uplinks but not all the way between two systems, then the end systems won't take any advantage of jumbo frames. There is no drawbacks of jumbo frames as such as far as I know, but some pitfalls.
Jumbo frames are any frames bigger than standard Ethernet frames (1518 bytes of user-visible part). And some platforms implement jambo frames as big as 9216 bytes (Cat 6500), while others (e.g. Cat 2950) are limited to baby-jumbo of 1530 bytes. So when you enable jumbo frames you must be sure that the size of jumbo frame is consistent across all your systems including servers and client PC's connected to your network.
Another pitfall is that if you enable jumbo frame on any IP-layer interface this will automatically change IP MTU. If you're running OSPF and jumbo frames are enabled only on some systems connected to a subnet but not on other systems from the same subnet OSPF adjacencies will not form until you specify 'ip mtu 1500' on jumbo-enabled systems. As soon as you do this, effect of jumbo frames for IP traffic will be void (but it might still be necessary for things like MPLS). So be sure that systems on common subnet have same MTU.
Routing problem is easy to detect, more general problem is that travelling across L2-only path there is no way for switches to send 'ICMP Fragmentation required' if packet is large then next interface MTU. This will break PMTU Discovery and since most applications usually sent packets at max MTU and DF-bit set, there will be timeouts. So again, consistent MTU across whole L2 path is important.
By the way, if your servers and PC's are not connected via jumbo-enabled links then you unlikely see any difference by enabling jumbo frames on the uplinks because both 6500 and 3550 catalysts are capable of wirespeed performance. The only time when it makes sense to enable jumbo frames only on the core links is when you need some non-IP headers to encapsulate your max-sized IP packets (MPLS is one such example).
As for benefits - servers running (very) heavy traffic applications (think full-feed USENET server with multiple fast peerings) may benefit from sending large portion of data in each packet, so for the same amount of data they need less number of packets. Destination system will have to handle less interrupts and overall performance may increase.
Hope this helps.

How do I maximize LAN speeds using Gigabit Ethernet, jumbo frames?

I move a lot of large files (RAW photos, music and video) around my internal network, and I'm trying to squeeze out the fastest transfer speeds possible. My question has to do both with decisions about hardware and what settings to use once it's all hooked up.
This is what I have so far:
-- imac 3.06GHz, macbook pro 2.53GHz
-- Cisco gigabit smart switch capable of jumbo frames
-- Buffalo Terastation Duo NAS (network attached storage), also capable of Gbit and jumbo frames
-- All wired up with either cat6 or cat53e.
-- The sizes of the files I'm moving would include large #s of files at either 15MB (photos), 7MB (music), 1-2GB (video) and 650MB (also video).
-- jumbo frames have been enabled in the settings of the macs, the switch and the buffalo HD.
-- I've played with various settings of simultaneous connections (more of a help with smaller files), no real difference
-- Network utility shows the ethernet set to Gbit, with no errors or collisions.
-- have tried both ftp and the finder's drap and drop
-- also, whenever I'm doing a major move of data, I kick my family off the network, so there is no other traffic that should be interfering.
Even with all that, I'm still lucky to get transfer speeds at 15-20mbps, but more commonly at around 10. The other odd thing I've encountered while trying to up my speeds, is that I might start out a transfer at maybe 60mbps, it will maintain that for about 30-60sec and then it appears to ramp itself down, sometimes to as low as 1-5mbps. I'm starting to think my network is mocking me
I also have a dual band (2.4/5) wireless n router (not jumbo frame capable), but I'm assuming wired is going to trump wireless? (NOTE: in my tests, I have disabled wireless to force the connection through the ethernet).
Can anyone help with suggestions, and/or suggest a strong networking reference book with emphasis on mac? I'm willing to invest in additional equipment within reason.
Thanks in advance!
juliana

I'm going to pick and choose to answer just a few of the items you have listed. Hopefully others will address other items.
• This setup was getting me speeds as high as 10-15MB/sec, and as low as 5-6MB/sec when I was transferring video files around 1-2 GB in size
I would think a single large file would get the best sustained transfer rates, as you have less create new file overhead on the destination device. It is disturbing that the large files transfer at a slower rate.
• Would a RAID0 config get me faster write speeds than RAID1? I have another NAS that can do other RAID configs, which is fastest as far as write times?
RAID0 (Striped) is generally faster, as the I/O is spread across 2 disks.
RAID1 is mirrored, so you can not free the buffer until the same data is on BOTH disks. The disks are NOT going to be in rotational sync, so at least one of the disks will have to wait longer for the write sectors to move under the write heads.
But RAID1 gives you redundency. RAID0 has not redundency. And you can NOT switch back and forth between the 2 without reformatting your disks, so if you choose RAID0, you do not get redundency unless you provide your own via a backup device for your NAS.
• what is the most efficient transfer protocol? ftp? smb? something else? And am I better off invoking the protocol from the terminal, or is the overhead of an app-based client negligible?
Test the different transfers using a large file (100's of MB or a GB sized file would be good as a test file).
I've had good file transfers with AFP file sharing, but not knowing anything about your NAS, I do not know if it supports AFP, and if it does, whether it is a good implementation.
If your NAS supports ssh, then I would try scp instead of ftp. scp is like using cp only it works over the network.
If your NAS support rsync, that would be even better, as it has the ability to just copy files that are either NOT on the destination or update files which have changed, but leave the matching files alone.
This would help in situations where you cannot copy everything all at once.
But no matter what you choose, you should measure your performance so you choose something that is good enough.
• If a client is fine, does anyone have a suggestion as to best one for speed? Doesn't have to be free -- I don't mind supporting good software.
Again just test what you have.
• Whats a good number to allow for simultaneous connections, given the number of files and their size?
If the bottleneck is the NAS, then adding more I/O that will force the disk heads to move away from the current file being written will just slow things down.
But try 2 connections and measure your performance. If it gets better, then maybe the NAS is not the bottleneck.
• What question am I not asking?
You should try using another system as a test destination device in the network setup to see if it gets better, worse, or the same throughput as the NAS. You need to see about changing things in your setup to isolate where the problem might be.
Also do not rule out bad ethernet cables, so switch them out as well. For example, there was a time I tried to use Gigabit ethernet, but could only get 100BaseT. I even purchased a new gigabit switch, thinking the 1st was just not up to the task. It turned out I had a cheap ethernet cable that only had 4 wires instead of 8 and was not capable of gigabit speeds. An ethernet cable that has a broken wire or connector could exhibit similar performance issues.
So change anything and everything in your setup, one item at a time and use the same test so you have a pear to pear comparision.

Catalyst 3750x and 4510R and Cisco Security Manager

Hi,
I just downloaded and install trial (evaluation) version of Cisco Security Manager 4.3. In supported devices list I saw Cisco Catalyst 3750 and 4510R but when I try to add it I got for 3750:
Invalid device: Device is a switch and cannot be mapped to a Generic Router model.
Please verify the selected device type, OS version and device configuration
For 4510R:
Invalid device: Version 03.03.00.SG (N/A) is not supported for the device type of Cisco Catalyst 4510R Switch Please verify the selected device type, OS version and device configuration
We need to make a purchase decision but for it we need to import all of our devices and perform some tests.
Thanks in advance for your replies!
BR, Vasily.

I figured this out on my own -- change Compatibility mode of the installer to be Windows 8 (which is same OS version as Windows 2012) and it installs just fine.

System FCS error frames on Catalyst 3750

Please,
may someone explain what are the "System FCS error frames" I see with "show controllers ethernet-controller" on some ports of a Catalyst (on trunk and also on access ports) WS-C3750G-24TS-S (3 switches in stackwyse)?
Error counters advance slowly, but they do grow... and I am afraid this could be the reason for variable slow access time to a server application menu...
For example "8 System FCS error frames".
The ports are connected to a PIX-515E and I see the same error count on the firewall interfaces (PIX "show interface" command shows me "8 input errors, 8 CRC, 0 frame, 0 overrun, 8 ignored, 0 abort")
A few errors may be seen also on other ports, connected to other (C3550)switches.
I tried to upgrade the IOS version, so I loaded "ipbase 12.2(25)SEB4 " on the Catalyst 3750, but it did not solve the problem.
PIX firewalls are running software 6.3(4).
Why these errors are called "System FCS error frames" ? I could not find anything searching on Cisco CCO!
Thanks

I apologies for the delay answering, my notebook has been down for 5 days and also cco access password...
Thank you for the explanation and suggestion.
We have a second rack with another three switch 4750 in stackwyse, same models as the "faulty" ones, and the errors are not present on those switches, so it must be something hardware related on the first group of switches.
I cannot touch those devices at the moment, we captured traffic frames with 3 Notebook PCs running "Ethereral" lan sniffer, traffic to and from the server and two clients and we discovered that in different ports of those switches, some packets never reach the clients, causing many TCP retransmissions, especially witch continuous traffic (http get and ftp transfers). This problem is visible on some, but not all, of the catalsyt 3750 switches in stackwyse, but in every one of the three switches. We are planning to go on-site and replace the hopefully faulty one ( or reseat the cables as you suggested).
Is this a problem you have seen before?
Regards
Franco Feri

Catalyst 3750 and jumbo frames

Similar Messages

Maybe you are looking for