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Packets bigger than 508 bytes getting dropped on MWR 1941 Multilink ERROR DROP_CAUSE_MLP_LINK_FRAGMENT

suhail.koul1
Level 1
Level 1

Hi 

I need help to understand why my packets bigger than 508 bytes are getting dropped.Due to this the Messages coming to the router which are fragmented are getting dropped . therror in the 

i am getting the error as below

Non-ZERO MLP Bundle Drop Stats Packets Bytes Bundle Index
DROP_CAUSE_MLP_LINK_FRAGMENT 9388 3608982 0

here is my config

PA-MEDIA#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 10.43.13.132 YES NVRAM up up
Serial0/0:0 unassigned YES NVRAM up up
FastEthernet0/1 5.5.5.5 YES NVRAM up down
Serial0/1:0 unassigned YES NVRAM down down
Multilink1 10.43.14.91 YES NVRAM up up
Virtual-Access1 unassigned YES unset down down
Virtual-Template1 unassigned YES NVRAM down down
Multilink2 unassigned YES NVRAM down down
Loopback1 10.10.10.10 YES manual up up
Loopback101 unassigned YES NVRAM up up
Loopback102 unassigned YES NVRAM up up
PA-MEDIA#

------------------ show running-config ------------------


Building configuration...

Current configuration : 1587 bytes
!
version 12.2
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname PA-MEDIA
!
boot system slot0:mwr1900-i-mz.122-15.MC2.bin
logging queue-limit 100
no logging console
!
!
redundancy
mode y-cable
!
ip subnet-zero
!
!
!
!
!
controller E1 0/0
clock source internal
channel-group 0 timeslots 1-31
!
controller E1 0/1
clock source internal
channel-group 0 timeslots 1-31
!
!
interface Loopback1
ip address 10.10.10.10 255.255.255.0
!
interface Loopback101
no ip address
!
interface Loopback102
no ip address
!
interface Multilink1
bandwidth 1984
ip address 10.43.14.91 255.255.255.0
no keepalive
no cdp enable
ppp multilink
multilink-group 1
!
interface Multilink2
no ip address
no keepalive
no cdp enable
ppp multilink
multilink-group 2
!
interface FastEthernet0/0
ip address 10.43.13.132 255.255.255.224
duplex auto
speed auto
!
interface Serial0/0:0
description Security_BTS
no ip address
encapsulation ppp
ppp multilink
ppp multilink endpoint ip 10.43.14.28
ppp multilink multiclass
multilink-group 1
!
interface FastEthernet0/1
ip address 5.5.5.5 255.255.255.0
duplex auto
speed auto
!
interface Serial0/1:0
description Security_BTS_66
no ip address
encapsulation ppp
ppp multilink
ppp multilink endpoint ip 10.43.14.124
ppp multilink multiclass
multilink-group 2
!
interface Virtual-Template1
no ip address
!
ip http server
ip classless
ip route 0.0.0.0 0.0.0.0 10.43.13.129
!
!
!
!
line con 0
password <removed>
login
line aux 0
line vty 0 4
password <removed>
login
!
end

4 Replies 4

Philip D'Ath
VIP Alumni
VIP Alumni

To me, because you have not configured an MTU this implies an MTU mismatch between you and the other end.  Ask the other end what they are using for their MTU and match their configuration.

Thanks Philip

I did set the MTU size to 1500 which is what is set on the BTS Side , I am still seing the error  DROP_CAUSE_MLP_LINK_FRAGMENT      . There is some issue here which I am not able to figure out , I just cleaned the config this time and removed all the unnecessary config on serial and Multilink .

interface Multilink1
 bandwidth 1984
 ip address 10.43.14.91 255.255.255.0
 no cdp enable
 ppp multilink
 multilink-group 1
end

PA-MEDIA#show run interface multilink 1           serial0/0:0
Building configuration...

Current configuration : 176 bytes
!
interface Serial0/0:0
 description Security_BTS
 no ip address
 encapsulation ppp
 no keepalive
 ppp multilink
 ppp multilink endpoint ip 10.43.14.28
 multilink-group 1
end

~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2016.03.10 11:04:14 =~=~=~=~=~=~=~=~=~=~=~=
show interface serial 0/0:0
Serial0/0:0 is up, line protocol is up
  Hardware is GT96K Serial
  Description: Security_BTS
  MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open, loopback not set
  Last input 00:02:23, output 00:02:23, output hang never
  Last clearing of "show interface" counters 00:11:07
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1000 bits/sec, 2 packets/sec
  5 minute output rate 1000 bits/sec, 1 packets/sec
     1250 packets input, 130524 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     20 input errors, 20 CRC, 7 frame, 0 overrun, 0 ignored, 7 abort
     1262 packets output, 126411 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     0 output buffer failures, 0 output buffers swapped out
     1 carrier transitions
  Timeslot(s) Used:1-31, SCC: 0, Transmitter delay is 0 flags
PA-MEDIA#show interface serial 0/0:0multilink 1 
Multilink1 is up, line protocol is up
  Hardware is multilink group interface
  Internet address is 10.43.14.91/24
  MTU 1500 bytes, BW 1984 Kbit, DLY 100000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open
  Listen: PPPMUXCP
  Open: IPCP, crc 16, loopback not set
  DTR is pulsed for 2 seconds on reset
  Last input 00:02:26, output never, output hang never
  Last clearing of "show interface" counters 00:11:10
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  5 minute input rate 1000 bits/sec, 2 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     1246 packets input, 130068 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     1250 packets output, 125439 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
PA-MEDIA#show ri un interf
PA-MEDIA#show run interface mul
PA-MEDIA#show run interface multilink 1
Building configuration...

Current configuration : 131 bytes
!
interface Multilink1
 bandwidth 1984
 ip address 10.43.14.91 255.255.255.0
 no cdp enable
 ppp multilink
 multilink-group 1
end

PA-MEDIA#show run interface multilink 1           serial0/0:0
Building configuration...

Current configuration : 176 bytes
!
interface Serial0/0:0
 description Security_BTS
 no ip address
 encapsulation ppp
 no keepalive
 ppp multilink
 ppp multilink endpoint ip 10.43.14.28
 multilink-group 1
end

PA-MEDIA#show run interface serial0/0:0multilink 1interface multilink 1    serial 0/0:0multilink 1 ping 10.43.14.28 size 508 10show run interface multilink 1ping 10.43.14.28 size 510     show run interface multilink 1conf t                        show run interface multilink 1serial 0/0:0conf t                         show run interface serial 0/0:0multilink 1                      interface multilink 1serial 0/0:0conf t                         show run interface serial 0/0:0multilink 1 conf t                        show run interface multilink 1ping 10.43.14.28 size 510       08

Type escape sequence to abort.
Sending 5, 508-byte ICMP Echos to 10.43.14.28, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/8 ms
PA-MEDIA#ping 10.43.14.28 size 508  10

Type escape sequence to abort.
Sending 5, 510-byte ICMP Echos to 10.43.14.28, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
PA-MEDIA#show pxf cpu statistics
PXF Drop Statistics

  Chassis Drop Stats                 Packets        Bytes
    DROP_CAUSE_BAD_DROP_CODE         0              0          
    DROP_CAUSE_INVALID_RESOURCE      0              0          
    DROP_CAUSE_ICMP_ON_ICMP          0              0          
    DROP_CAUSE_IPC_CMD_INVALID       0              0          
    DROP_CAUSE_ICMP_UNRCH_INTERVAL   1              77         
    DROP_CAUSE_NO_TOUCH_FROM_RP      0              0          
    DROP_CAUSE_DST_IP_IS_MCAST       0              0          
    DROP_CAUSE_ENCAP_TOO_BIG         0              0          
    DROP_CAUSE_ICMP_FRAG             0              0          
    DROP_CAUSE_BAD_MAC_ENTRY         0              0          
    DROP_CAUSE_ENQ_TO_NULL_QID       0              0          

  Resource Drop Stats                Packets        Bytes          Resource
    DROP_CAUSE_NULL_CONFIG           0              0              (all)

  Interface Drop Stats               Packets        Bytes          Interface
    DROP_CAUSE_VCCI_UNDEFINED        0              0              (all)

  Non-ZERO VCCI Drop Stats           Packets        Bytes          VCCI
    DROP_CAUSE_UNREACHABLE           3              255            64

  Non-ZERO MLP Bundle Drop Stats     Packets        Bytes          Bundle Index
    DROP_CAUSE_MLP_LINK_FRAGMENT     49             12658          0

  Non-ZERO Queue Drop Stats          Packets        Bytes          QID
    None

  IP Statistics                      Packets
    dropped                          0
    forwarded                        2809
    diverted                         71
    input_packets                    2883
    icmps_created                    3
    noadjacency                      0
    noroute                          3
    unicast_rpf                      0
    unresolved                       0

  IP Frag Statistics                 Packets
    dont_frag                        0
    divert_frag                      0

  ICMP Statistics                    Packets
    unreachsent                      2
    ttlsent                          0
    echorepsent                      0
    echorcv                          0
    checksumerr                      0

  MLP Reorder Per-chassis Stats      Packets
    mlp_err_c1_overwrite             0          

  Divert Statistics                  Packets
    DIV_CAUSE_LOCAL_ADDRESS          71         
    DIV_CAUSE_IP_OPT                 0          
    DIV_CAUSE_ENCAP_NOT_SUPPORTED    14         
    DIV_CAUSE_FR_LMI                 0          
    DIV_CAUSE_ARP                    37         
    DIV_CAUSE_RARP                   0          
    DIV_CAUSE_DIVERT_ALL             0          
    DIV_CAUSE_IGMP                   0          
    DIV_CAUSE_MULTICAST              0          
    DIV_CAUSE_MULTICAST_PROTOCOL     0          
    DIV_CAUSE_KEEPALIVE              0          
    DIV_CAUSE_MIN_MTU                0          
    DIV_CAUSE_ICMP_FRAG              0          
    DIV_CAUSE_ICMP_BAD_HDR           0          
    DIV_CAUSE_CLNS_ISIS              0          
    DIV_CAUSE_PPP_CNTRL              6          
    DIV_CAUSE_IP_FRAG                0          
    DIV_CAUSE_CRTP_TO_RP             0          
    DIV_CAUSE_ROUTE_RESOLUTION       0          
    Invalid DIV_CAUSE                0          
PA-MEDIA#

Just to add the error is same as Packets bigger than 508 bytes is getting dropped. The setup is as below

            BTS <--------E1--------> MWR 1941<------------------FE----------->BSC

Packet Drops happen when the size of packets from BTS are Greater than 508 Bytes , From BSC to BTS no Drops are seen

I wonder if one link has an issue.

Try doing the ping with only one link up at a time, and see if the issue happens on both links.

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