| Best IOS for 1801W I'm running 12.4(15)T13 on my 1801W.
It's stable, but there are a couple of issues:
= downloads from the internet are sometimes perfect (1.75Mb/s) and sometimes peter out part way through the download, for no reason that I can see. It did not used to happen.
= Cisco Configuration Professional 2.x does not see all of my interfaces, for some reason.
Should I just install 12.4(15)T14 or is a higher release preferable? (I don't really use any of the fancier features other than VPN L2TP/IPSec.)
I suspect that my maintenance contract will have run out, if that makes any difference. |
|
bigsy
join:2001-07-18
UK
kudos:1 | said by godrick :
= downloads from the internet are sometimes perfect (1.75Mb/s) and sometimes peter out part way through the download, for no reason that I can see. It did not used to happen.
Have you done any troubleshooting of the ADSL connection whenever this happens?
If you're in the UK (judging by your email), has your local BT exchange been upgraded recently?
If you haven't already done so, it might be worthwhile putting on newer ADSL firmware as there have been problems with BT's kit. |
|
|
|
| reply to godrick
you need to include your cards if you are talking about releases... T lines are NOT preferred and you also need to see if your issues are solved in the new release code. |
|
 rolandeCertifiablePremium,Mod
join:2002-05-24
Columbus, OH | reply to godrick
Are you using the 'ip inspect' feature in the IOS firewall? If so, you will need to load up something newer than 12.4(11)T to handle out of order packets. |
|
| Thanks for these responses.
I am on BeUnlimited, so did not use the more recent firmware which seems to be for BT problems.
I am using the inspection / ZBF that Configuration Professional configures in.
The syslog does not seem to reveal anything interesting when the downloads stall, and it does not always seem to happen.
It's an 1801w, so there are no extra cards.
I did try the 15.x series when they first came but they crashed the router as it booted, so I went back to 12.4(15)Tx which was MD and seems stable, apart from these recent issues. |
|
| reply to godrick
ZBFW does have issues with out of order packets, which isn't fixed till 15.1, IIRC. About the only two
ways I can think of to catch if this is router logs (if you're logging this) or a packet sniffer. A
surefire way to rule out the router / IOS is use your existing config between two PCs, one simulating
a LAN PC and the other simulating the WAN and trying to replicate the problem.
Would you be willing to share your config as well?
Regards |
|
| Here is the config.
I have also tried adding mtu 1500 to the atm interface, with no improvement. |
|
| reply to godrick
Think you may also want to try lower MTU values like 1480 or lower, in case
fragmentation is messing with your packets. I don't see anything wierd and
whacky with your config so far...
Regards |
|
rolandeCertifiablePremium,Mod
join:2002-05-24
Columbus, OH Host:
Linksys
AT&T Midwest
| If you are running PPPoE on an ATM/DSL interface, I would recommend setting 'ip tcp adjust-mss 1452' on the ethernet interface connecting to your home network. 1452 bytes is the magic segment size that doesn't cause inefficient fragmentation across the DSL interface. This maximizes your overall ability to move data in the largest chunks possible and effectively reduces any serialization delay due to ATM cell stuffing. So the effective MTU is 1492 which includes the 40 byte IP header.
--
Scott, CCIE #14618 Routing & Switching
Too bad those that know it all can't do it all.
»www.thewaystation.com/techref/tech.shtml
»blog.thewaystation.com/ |
|
| reply to godrick
Was there a doc somewhere that explained why on DSL configs it's recommended to adjust your
MSS to 1452? I recall that's like an SOP, but I forget the nuts and bolts details why you
need that for most DSL configs.
Regards |
|
cramer
join:2007-04-10
Raleigh, NC
kudos:5 Reviews:
 ·AT&T Southeast
| said by HELLFIRE:Was there a doc somewhere... From Cisco? Doubt it. (if it's in any example configs, I doubt it's explained.)
Basically the math goes like this... Ethernet MTU = 1500. PPP header is 8. IP header is 40. 1500 - 8 - 40 == 1452 MSS. The max amount of user data that can fit in a single packet.
However, with an ATM (AAL5) physical layer, the most efficient setup is slightly less. The ATM cell is 53 bytes. AAL5 eats 5 of them, leaving 48 for real data. 1500/48 = 31.25. Avoiding the padding of a partial cell, that's an MTU of [48*31] 1488... 1488 - 8 - 40 == 1440 MSS.
PPPoA ... etc.
(This is what I call Networking Voodoo(tm).) |
|
1 edit | reply to godrick
I know there is a Cisco doc on changing the MTU to 1492 for PPPoE and they give you a brief description of why. But it is a pretty "basic" document and lacks much detail. |
|
| reply to godrick
Well, I have changed the MTU/MSS to 1500/1460 but no improvement, I'm afraid |
|
| reply to godrick
I've recently switched all my 800-series routers to 15.0.1M3 save for an 871W which didn't have the flash space, so it is on 12.4.24T3.
I would try the 15.0.1M3 release and see what happens just for fun. |
|
| Did you have to do anything to the config or did you just reload with the new image? |
|
| The only one I had issue with was one with wireless. The others "just worked". |
|
rolandeCertifiablePremium,Mod
join:2002-05-24
Columbus, OH Host:
Linksys
AT&T Midwest
| reply to cramer
said by cramer:However, with an ATM (AAL5) physical layer, the most efficient setup is slightly less. The ATM cell is 53 bytes. AAL5 eats 5 of them, leaving 48 for real data. 1500/48 = 31.25. Avoiding the padding of a partial cell, that's an MTU of [48*31] 1488... 1488 - 8 - 40 == 1440 MSS. AAL5 actually eats 5 bytes of header in each cell plus an 8 byte trailer on the last cell of the chopped up ethernet frame. If your math is off, you get an additional cell at the very end with 40 bytes of padding and an 8 byte trailer plus the 5 bytes of header.
If you want to be as efficient as possible, you would set your MSS to 1432 to avoid the extra cell with the AAL5 trailer and 40 bytes of padding.
1452 = MSS for the payload of an IP packet encapsulated in PPPoE traversing an ethernet interface.
1452 MSS / 48 Byte ATM payload = 30.25 ATM cells
To avoid the partial ATM cell...
30ATM cells * 48 bytes payload = 1440 bytes
However, you need to subtract the final 8 byte trailer to avoid the dangling ATM cell.
So, MSS = 1432 bytes if you want to be technical about configuring it in the most efficient manner possible.
--
Scott, CCIE #14618 Routing & Switching
Too bad those that know it all can't do it all.
»www.thewaystation.com/techref/tech.shtml
»blog.thewaystation.com/ |
|
| reply to OVERKILL
So far so good with 15.0.3M. A couple of sites from which I failed to download with 12.4.15T13 worked.
What was the wireless issue, before I stumble over it?
I think that I may reconfigure from scratch using CCP 2.3, rather than relying on the SDM-generated config with which I started. |
|
| If your wireless is working, you don't have the issue  |
|
| Oh I see. Having tried to configure from scratch, the Wireless now wants a VLAN and produces subinterfaces, etc.
Is there a pointer to a simple config? |
|
