async dialup to internet mtu? problem

[thunderbug66]

hi all,
i found a script on an ealier thread to use a cisco router to dialup to the internet over isdn. i modified it to work using async modems and everything works fine until i try to use a web browser. ping, telnet, mail, dns, etc.. works perfectly, but web browsing causes everything to stop. i suspected an mtu problem, and lowering the mtu and ip mtu settings on the interfaces does prevent whatever is causing the crash, but i still cannot use the web browser. any ideas?? scripts and dubug output follow.

thanks!
--jel

Cisco Internetwork Operating System Software
IOS (tm) 1600 Software (C1600-Y-L), Version 11.3(3)T, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1998 by cisco Systems, Inc.
Compiled Mon 20-Apr-98 19:48 by ccai
Image text-base: 0x08022C58, data-base: 0x02005000

ROM: System Bootstrap, Version 11.1(10)AA, EARLY DEPLOYMENT RELEASE SOFTWARE (fc
1)
ROM: 1600 Software (C1600-BOOT-R), Version 11.1(10)AA, EARLY DEPLOYMENT RELEASE
SOFTWARE (fc1)

Dialup-test uptime is 2 days, 18 hours, 33 minutes
System restarted by reload
System image file is "flash:80269401.bin", booted via flash

cisco 1601 (68360) processor (revision C) with 1536K/512K bytes of memory.
Processor board ID 10545782, with hardware revision 00000000
Bridging software.
X.25 software, Version 3.0.0.
1 Ethernet/IEEE 802.3 interface(s)
2 serial(sync/async) network interface(s)
System/IO memory with parity disabled
2048K bytes of DRAM onboard
System running from FLASH
8K bytes of non-volatile configuration memory.
4096K bytes of processor board PCMCIA flash (Read ONLY)

Configuration register is 0x2102

Current configuration:
!
version 11.3
service password-encryption
!
hostname Dialup-test
!
ip subnet-zero
no ip source-route
ip nat inside source list 101 interface Dialer1 overload
no ip domain-lookup
chat-script dial ABORT BUSY ABORT ERROR "" "ATDT \T" TIMEOUT 60 CONNECT \c
!
!
interface Ethernet0
ip address 192.168.10.1 255.255.255.0
no ip proxy-arp
ip nat inside
!
interface Serial0
physical-layer async
no ip address
encapsulation ppp
dialer in-band
dialer pool-member 1
async mode dedicated
no fair-queue
no cdp enable
ppp authentication chap pap ms-chap callin
ppp multilink
!
interface Serial1
no ip address
shutdown
!
interface Dialer1
ip address negotiated
no ip proxy-arp
ip nat outside
encapsulation ppp
no ip split-horizon
dialer remote-name Cisco1
dialer idle-timeout 360
dialer string <phonenum>
dialer hold-queue 10
dialer load-threshold 10 outbound
dialer pool 1
dialer-group 1
no cdp enable
ppp authentication chap pap ms-chap callin
ppp pap sent-username <username> password 7 <password>
ppp multilink
!
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer1 permanent
!
map-class dialer DialClass
dialer wait-for-carrier-time 65
access-list 101 permit ip 192.168.10.0 0.0.0.255 any
dialer-list 1 protocol ip permit
dialer-list 2 protocol ip list 100
!
line con 0
line 1
script dialer dial
modem InOut
transport input all
speed 115200
flowcontrol hardware
line vty 0 4
password 7 <pass>
login
!
end

debug ppp auth and ppp neg on dialup:
%LINK-3-UPDOWN: Interface Serial0, changed state to up
%DIALER-6-BIND: Interface Serial0 bound to profile Dialer1
Se0 PPP: Treating connection as a callout
Se0 PPP: Phase is ESTABLISHING, Active Open
Se0 PPP: No remote authentication for call-out
Se0 LCP: O CONFREQ [Closed] id 12 len 38
Se0 LCP: ACCM 0x000A0000 (0x0206000A0000)
Se0 LCP: MagicNumber 0x1EC37163 (0x05061EC37163)
Se0 LCP: PFC (0x0702)
Se0 LCP: ACFC (0x0802)
Se0 LCP: MRRU 1524 (0x110405F4)
Se0 LCP: EndpointDisc 1 Local (0x130E014469616C75702D74657374)
Se0 LCP: I CONFREQ [REQsent] id 1 len 43
Se0 LCP: VendorSpecific OUI 0x000001 (0x00040000)
Se0 LCP: MRU 1524 (0x010405F4)
Se0 LCP: ACCM 0x000A0000 (0x0206000A0000)
Se0 LCP: AuthProto PAP (0x0304C023)
Se0 LCP: PFC (0x0702)
Se0 LCP: ACFC (0x0802)
Se0 LCP: MRRU 1524 (0x110405F4)
Se0 LCP: EndpointDisc 3 00d0.5204.9428 (0x13090300D052049428)
Se0 LCP: Type27 (0x1B040202)
Se0 LCP: O CONFREJ [REQsent] id 1 len 12
Se0 LCP: VendorSpecific OUI 0x00001B (0x00040000)
Se0 LCP: Type27 (0x1B040202)
Se0 LCP: I CONFACK [REQsent] id 12 len 38
Se0 LCP: ACCM 0x000A0000 (0x0206000A0000)
Se0 LCP: MagicNumber 0x1EC37163 (0x05061EC37163)
Se0 LCP: PFC (0x0702)
Se0 LCP: ACFC (0x0802)
Se0 LCP: MRRU 1524 (0x110405F4)
Se0 LCP: EndpointDisc 1 Local (0x130E014469616C75702D74657374)
Se0 LCP: I CONFREQ [ACKrcvd] id 2 len 35
Se0 LCP: MRU 1524 (0x010405F4)
Se0 LCP: ACCM 0x000A0000 (0x0206000A0000)
Se0 LCP: AuthProto PAP (0x0304C023)
Se0 LCP: PFC (0x0702)
Se0 LCP: ACFC (0x0802)
Se0 LCP: MRRU 1524 (0x110405F4)
Se0 LCP: EndpointDisc 3 00d0.5204.9428 (0x13090300D052049428)
Se0 LCP: O CONFACK [ACKrcvd] id 2 len 35
Se0 LCP: MRU 1524 (0x010405F4)
Se0 LCP: ACCM 0x000A0000 (0x0206000A0000)
Se0 LCP: AuthProto PAP (0x0304C023)
Se0 LCP: PFC (0x0702)
Se0 LCP: ACFC (0x0802)
Se0 LCP: MRRU 1524 (0x110405F4)
Se0 LCP: EndpointDisc 3 00d0.5204.9428 (0x13090300D052049428)
Se0 LCP: State is Open
Se0 PPP: Phase is AUTHENTICATING, by the peer
Se0 PAP: O AUTH-REQ id 12 len 22 from &quot;<username>&quot;
Se0 PAP: I AUTH-ACK id 12 len 5
Se0 PPP: Phase is VIRTUALIZED
Se0 MLP: PPP phase is VIRTUALIZED, discarding packet
Vi1 PPP: Phase is DOWN, Setup
%DIALER-6-BIND: Interface Virtual-Access1 bound to profile Dialer1
Se0 MLP: PPP phase is VIRTUALIZED, discarding packet
%LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up
Vi1 PPP: Treating connection as a callin
Vi1 PPP: Phase is ESTABLISHING, Passive Open
Vi1 LCP: State is Listen
Vi1 PPP: Phase is UP
Vi1 IPCP: O CONFREQ [Closed] id 1 len 10
Vi1 IPCP: Address 0.0.0.0 (0x030600000000)
Vi1 IPCP: I CONFNAK [REQsent] id 1 len 10
Vi1 IPCP: Address 66.44.114.18 (0x0306422C7212)
Vi1 IPCP: O CONFREQ [REQsent] id 2 len 10
Vi1 IPCP: Address 66.44.114.18 (0x0306422C7212)
Vi1 IPCP: I CONFACK [REQsent] id 2 len 10
Vi1 IPCP: Address 66.44.114.18 (0x0306422C7212)
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to up
Vi1 IPCP: TIMEout: Time 0xE478F48 State ACKrcvd
Vi1 IPCP: O CONFREQ [ACKrcvd] id 3 len 10
Vi1 IPCP: Address 66.44.114.18 (0x0306422C7212)
Vi1 IPCP: I CONFACK [REQsent] id 3 len 10
Vi1 IPCP: Address 66.44.114.18 (0x0306422C7212)
Vi1 IPCP: I CONFREQ [ACKrcvd] id 1 len 16
Vi1 IPCP: CompressType VJ 15 slots CompressSlotID (0x0206002D0F01)
Vi1 IPCP: Address 208.59.89.144 (0x0306D03B5990)
Vi1 IPCP: O CONFREJ [ACKrcvd] id 1 len 10
Vi1 IPCP: CompressType VJ 15 slots CompressSlotID (0x0206002D0F01)
Vi1 CCP: I CONFREQ [Not negotiated] id 2 len 10
Vi1 CCP: Stacker history 1 check mode LCB (0x110600010103)
Vi1 LCP: O PROTREJ [Open] id 1 len 16 protocol CCP (0x80FD0102000A110600010103)
Vi1 IPCP: I CONFREQ [ACKrcvd] id 2 len 10
Vi1 IPCP: Address 208.59.89.144 (0x0306D03B5990)
Vi1 IPCP: O CONFACK [ACKrcvd] id 2 len 10
Vi1 IPCP: Address 208.59.89.144 (0x0306D03B5990)
Vi1 IPCP: State is Open
Di1 IPCP: Install negotiated IP interface address 66.44.114.18
Di1 IPCP: Install route to 208.59.89.144

after using the web browser:
Vi1 PPP: Unsupported or un-negotiated protocol. Link cdp
Vi1 UNKNOWN(0x0000): I VENDORS [Not negotiated] id 0 len 0
Vi1 LCP: O PROTREJ [Open] id 2 len 1500 protocol UNKNOWN(0x0000)
Vi1 LCP: (0x00000000000000000000000000000000)
Vi1 LCP: (0x00000000000000000000000000000000)
<duplicate lines snipped>
Vi1 UNKNOWN(0x0000): I VENDORS [Not negotiated] id 0 len 0
Vi1 LCP: O PROTREJ [Open] id 3 len 1500 protocol UNKNOWN(0x0000)
Vi1 LCP: (0x00000000000000000000000000000000)
Vi1 LCP: (0x00000000000000000000000000000000)
<duplicate lines snipped>
Vi1 UNKNOWN(0x0000): I VENDORS [Not negotiated] id 0 len 0
Vi1 LCP: O PROTREJ [Open] id 4 len 1500 protocol UNKNOWN(0x0000)
Vi1 LCP: (0x00000000000000000000000000000000)
Vi1 LCP: (0x00000000000000000000000000000000)

 

[thunderbug66]

so... does anyone out there have a clue about this problem??

 

[routerman]

Its a pity the IOS is so old, later images have a feature which allows the TCP segment size to be modified during the 3 way handshake at set up time.

When the router crashes, what state does it go to, can you still access it via telnet?

 

[thunderbug66]

i managed to borrow a 1760 with 12.2(15)T2. it does pretty much the same thing, although slightly better. some pages come up (google, some google searches). but, on the debug, i see &quot;S1/0 I packet too large size 1506 maxsize 1504&quot; several times before the the LCP unknown protocol messages. i tried changing the mtu and ip mtu settings on the 1760 with no better results. any other settings or debugs that i can try?

thanks!
--jel

 

[routerman]

Try using the interface command `ip tcp mss-adjust 1400'

This tells the router to sniff the negotiated TCP mss size in the tcp set up negotiation and set it to 1400. If that works you can adjust the value to get the best for your application. If this dosent fix it I dont think the problem is down to MTU.

 

[thunderbug66]

thanks routerman! the router did not have the 'ip tcp mss-adjust' command but it did have 'ip tcp mss' so i set that to 1400. now i still get all the errors, both LCP PROTREJ and packet too large errors, but the system continues to work and pages are downloaded correctly. do you think the errors still being there is something to worry about? this seems like a fairly common application...

--jimmy

 

[routerman]

Jimmy,

I agree this must be a pretty common application, although I've never used the async modems in Cisco routers. Looking at the debug putput it seems that when the web browser is started you get large packets of all 0's. Also the first message posted above after you started the web browser mentions `Unsupported or un-negotiated protocol. Link cdp'

Have you tried a different PC web browser? I'm thinking that there may be a problem with the browser, its generating duff packets for some reason?

Any way at least you have a partial fix, but I would be concerned about the error messages, must be an indication of another problem. As you have swapped the router I would suspect an external cause.