LCP timeout on PPP link

Unanswered Question

Hi folks,

Getting a Interface up, line protocol down. Link used to work fine. Line has been tested by ISP. Appears PPP negotiation is failing:

Router 1: Se0 LCP: TIMEout: State ACKsent

Router 2: Se0 LCP: TIMEout: State REQsent

Any ideas? Both have the same encapsulation and are using ESF/B8ZF. Power cycling does nothing.



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Richard Burts Fri, 08/24/2007 - 08:50
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I would look at the possibility of a problem on the line which interrupts transmission in one direction. It looks to me like Router2 has transmitted to negotiate the link (REQsent) and like Router1 has sent an acknowledgement but Router2 does not receive what Router1 is sending.



Richard Burts Fri, 08/24/2007 - 09:43
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In terms of ways to test you might think about these alternatives:

- perhaps the packet counters in show interface might be helpful. You could try this: clear interface counters on both interfaces, wait a while while the link is attempting to negotiate, do show interface and look at packets out and packets in on both interfaces. Is there much mismatch between sent from Router2 to received on Router1 (and in the other direction also)?

- perhaps debug ppp negotiation (on both routers) might show one router sending and receiving while the other router is sending but not receiving?

- you might try debug serial interface and see if it gives you anything helpful.

- you might try configuring both router interfaces for HDLC encapsulation instead of PPP. The debug showing the HDLC yourseen and myseen might show whether there is one way traffic in one direction.



sdoremus33 Fri, 08/24/2007 - 09:26
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Have you checked the line(See Below T-Shooting cmds .Also are you running a clock rate at the DTE end of the line, did you set the clockrate to internal


config t


clockrate internal, or did you specify the clock rate instead using above config with clockrate 64000(@the DTE end of the cable)

also the clock rate command is used @ the DTE end of the cable Use the following t-Shoting cmds



SH IP INT S0 "Or whatever interface used to connect to the other router.

Take care HTH.


Clock source is specified by the line. The WICs include integrated CSU/DSU modules too FYI. Output (note # substituted for IPs):

Corp#sh ip int s0

Serial0 is up, line protocol is down

Interface is unnumbered. Using address of FastEthernet0 (#)

Broadcast address is

MTU is 1500 bytes

Helper address is not set

Directed broadcast forwarding is disabled

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is enabled

Security level is default

Split horizon is enabled

ICMP redirects are always sent

ICMP unreachables are always sent

ICMP mask replies are never sent

IP fast switching is enabled

IP fast switching on the same interface is enabled

IP Fast switching turbo vector

IP multicast fast switching is disabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast

Router Discovery is disabled

IP output packet accounting is disabled

IP access violation accounting is disabled

TCP/IP header compression is disabled

RTP/IP header compression is disabled

Probe proxy name replies are disabled

Policy routing is disabled

Network address translation is disabled

WCCP Redirect outbound is disabled

WCCP Redirect exclude is disabled

BGP Policy Mapping is disabled

Corp#sh ip int br

Interface IP-Address OK? Method Status Prot


FastEthernet0 # YES NVRAM up up

Serial0 # YES unset up down

Serial1 # YES unset up up

Corp#sh controllers serial 0

Interface Serial0

Hardware is PowerQUICC MPC860 with Integrated FT1 CSU/DSU module

TX and RX clocks detected.

idb at 0x80920A28, driver data structure at 0x80926DB8

SCC Registers:

General [GSMR]=0x2:0x00000030, Protocol-specific [PSMR]=0x8

Events [SCCE]=0x0300, Mask [SCCM]=0x001F, Status [SCCS]=0x02

Transmit on Demand [TODR]=0x0, Data Sync [DSR]=0x7E7E

Interrupt Registers:

Config [CICR]=0x00365F80, Pending [CIPR]=0x00008800

Mask [CIMR]=0x60204400, In-srv [CISR]=0x00000000

Command register



Rx BD Base [RBASE]=0x2230, Fn Code [RFCR]=0x18

Tx BD Base [TBASE]=0x22B0, Fn Code [TFCR]=0x18

Max Rx Buff Len [MRBLR]=1548

Rx State [RSTATE]=0x0, BD Ptr [RBPTR]=0x2230

Tx State [TSTATE]=0x0, BD Ptr [TBPTR]=0x22B0


CRC Preset [C_PRES]=0xFFFF, Mask [C_MASK]=0xF0B8

Errors: CRC [CRCEC]=0, Aborts [ABTSC]=0, Discards [DISFC]=0

Nonmatch Addr Cntr [NMARC]=0

Retry Count [RETRC]=0

Max Frame Length [MFLR]=1608

Rx Int Threshold [RFTHR]=0, Frame Cnt [RFCNT]=10193

User-defined Address 0000/0000/0000/0000

User-defined Address Mask 0x0000

buffer size 1524

PowerQUICC SCC specific errors:

4596 input aborts on receiving flag sequence

0 throttles, 0 enables

0 overruns

0 transmitter underruns

0 transmitter CTS losts



sundar.palaniappan Fri, 08/24/2007 - 10:27
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If you rebooted both routers then there's a good chance Router1's WIC CSU/DSU might be faulty as the ACK packets sent by Router1 isn't making it to Router2. Can you try swapping the WIC on Router1?



Mohamed Sobair Sat, 08/25/2007 - 00:00
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Hi Jeff,

could you try shutting down both interfaces, also double check the encapsulatiom , compression type or Authentication if any..

if the problem exist , please issue the (debug ppp negotiation) privilege command & post the output.


Mohamed Sobair

purohit_810 Tue, 08/28/2007 - 09:28
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Please check at boh end... CHAP and PAP authentication.. basically it is authentication issue.




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