TCP Window Scaling issue with 1811 router running IOS 12.3(8)YI1
Does the 1811 router (mine came with IOS 12.3(8)YI1 installed) have an issue with NAT and tcp window scaling? After testing my home Belkin Pre-N router (Model F5D8230-4) I get the full bandwidth expected. I'm guessing this is either due to using an older IOS image or my configuration but I have to admit I'm having an awfully difficult time figuring anything out on Cisco's website.
My bandwith from my linux machines drop to about 20% of normal with the 1811 router we purchased after upgrading to kernels 2.6.17 through 2.6.18-rc4. I was finally able to track the problem to a changed default tcp window scaling setting that modified my machines' tcp window scaling setting to a wscale of 7 in linux 2.6.16-git10.
Setting /proc/sys/net/ip4v/tcp_window_scaling to 0 on the linux machines restores bandwidth to about normal, but this seems to be against linux kernel developers recommendations and their recommended advice is to correct the affected router and they think the most likely cause is my NAT implementation.
If it is more than likely an outdated IOS issue, how does one go about getting an upgrade? Does Cisco provide upgrades in this case? I do not have a support contract, but I did purchase the router within the last year if that matters. If it does not matter, how does one get a support contract to get the IOS?
First of all, you cannot ask people to provide the support contract to you. You need to obtain it from your Cisco reseller.
For your question, please try to check below link for the information to configure the tcp window scaling. It is supported since 12.2, I believe your IOS is not outdated. Just via http://www.cisco.com/go/fn and find the min. IOS is 12.3(8) YI1 w/ Advanced IP Services Feature. You need to ensure you are running Advanced IP Services then try the command. If it is not the specific feature set, you have to contact the Cisco reseller to get it.
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