ARP issue

[Imran Ahmad]

Hello Experts,

I have around 500 clients computers connected through a Cisco Switch.  I have also multiple VLANs created.

there is an issue,  after each 10-mins the connectivity between vlans gets lost.   unless I run the command  CLEAR ARP on my switch the connections do not come back.

Can any one help me plz,  what can be the issue.  if it is the ARP Table size issue? can I increase the size ?  plz instruct me

Regards,

Waheed

[InayathUlla Sharieff]

Waheed,

What is the Hardware and software of the Switch?

How many vlans have you configured?

Is this new setup?

How many total devices are there?

Regards

Inayath

[Imran Ahmad]

Hi,

It is Cisco Cat 3750G,  Cisco IOS Software, C3750 Software (C3750-IPBASE-M), Version 12.2(50)SE5, RELEASE SOFTWARE

I have created 4 VLANs.

Yes it is new setup, and total computers will be around 500

Regards,

[Imran Ahmad]

Any help ?

[InayathUlla Sharieff]

Imran,

We need to look more into this:-

1- Currently how many users are active and faicng the issue?

2- What exactly you mean by losing the switch? User to Switch/User communication ont happeing?

3- Is User A in one vlan not able to ping User B of smae/.other vlan?

4- Do you see the MAC entry getting flushed out during the issue?

HTH

Regads

Inayath

[Imran Ahmad]

1- 400-500 Users are active and facing this issue frequently after each 10-min

2- User to Switch (Gateway) communication gets lost after each 10-min

3- The connections are not lost in-between users in same vlan subnet, but the connection loses between different subnets

4- YES I do see the MAC entry getting flushed out during the issue. (sho ip are | in 192.168..x.x)

Regards,

Waheed

[InayathUlla Sharieff]

mac addresses can disappear from CAM table if MAC table gets flushed. It gets fushed when STP TC's (Topology Change) occur following network reconvergence/link flappings.

+ By default the arp timeout is 4 hours and mac address table timeout is 300 seconds. 

Can you give me the output of:-

show int vlan X(X-=replace with one of your number)
show mac address-table aging-time
show span det | in ieee|from|occur|is exec

[Imran Ahmad]

Roshan-Switch#sho mac address-table aging-time
Global Aging Time:  300
Vlan    Aging Time
----    ----------
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#sho sp
Roshan-Switch#sho spanning-tree det | in ieee|from|occur|is exec
 VLAN0690 is executing the ieee compatible Spanning Tree protocol
  Number of topology changes 0 last change occurred 00:04:47 ago
 VLAN0691 is executing the ieee compatible Spanning Tree protocol
  Number of topology changes 0 last change occurred 00:04:47 ago
 VLAN0692 is executing the ieee compatible Spanning Tree protocol
  Number of topology changes 0 last change occurred 00:04:47 ago
 VLAN0695 is executing the ieee compatible Spanning Tree protocol
  Number of topology changes 4 last change occurred 00:01:39 ago
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#sho int vlan 690
Vlan690 is up, line protocol is up
  Hardware is EtherSVI, address is 6c50.4d94.78c8 (bia 6c50.4d94.78c8)
  Description: MPLS_Mazar_Region_Branches (Mzr1,Mzr2,Khulm,Smng,Balkh,Sholgra,Shb,Sarpul,Aqcha,
oi,Maimana)
  Internet address is 192.168.38.2/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 00:00:10
  Last input 00:00:00, output 00:00:23, output hang never
  Last clearing of "show interface" counters never
  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 2000 bits/sec, 3 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     9500 packets input, 906810 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     1890 packets output, 139354 bytes, 0 underruns
     0 output errors, 1 interface resets
     0 output buffer failures, 0 output buffers swapped out
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#sho int vlan 691
Vlan691 is up, line protocol is up
  Hardware is EtherSVI, address is 6c50.4d94.78c9 (bia 6c50.4d94.78c9)
  Description: MPLS_Kunduz_Region_Branches (Doshi,PLK,Kunduz,Takhar,Kishm,Fzd,Baharak,Jurm)
  Internet address is 192.168.26.2/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 00:00:10
  Last input 00:00:00, output 00:00:01, output hang never
  Last clearing of "show interface" counters never
  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 11000 bits/sec, 15 packets/sec
  5 minute output rate 12000 bits/sec, 14 packets/sec
     31713 packets input, 2716943 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     24344 packets output, 2157018 bytes, 0 underruns
     0 output errors, 1 interface resets
     0 output buffer failures, 0 output buffers swapped out
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#sho int vlan 692
Vlan692 is up, line protocol is up
  Hardware is EtherSVI, address is 6c50.4d94.78ca (bia 6c50.4d94.78ca)
  Internet address is 192.168.7.2/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 00:00:10
  Last input 00:00:00, output 00:00:04, output hang never
  Last clearing of "show interface" counters never
  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, 1 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     6404 packets input, 533264 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     1050 packets output, 74362 bytes, 0 underruns
     0 output errors, 1 interface resets
     0 output buffer failures, 0 output buffers swapped out
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#
Roshan-Switch#sho int vlan 695
Vlan695 is up, line protocol is up
  Hardware is EtherSVI, address is 6c50.4d94.78cb (bia 6c50.4d94.78cb)
  Description: E1_Branches(JLB,KK,KS,Mandavi,Taimani,Charikar,Jabelsaraj,Bamyan,Yakawlang,Panja
  Internet address is 192.168.27.2/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 00:00:10
  Last input 00:00:02, output 00:00:02, output hang never
  Last clearing of "show interface" counters never
  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 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     8249 packets input, 772736 bytes, 0 no buffer
     Received 0 broadcasts (94 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     3701 packets output, 296002 bytes, 0 underruns
     0 output errors, 2 interface resets
     0 output buffer failures, 0 output buffers swapped out
Roshan-Switch#

[InayathUlla Sharieff · Accepted solution]

Can you try chaing the ARP timeout values on one of the interface and chck?

example:

int vlan x

(config-if)#arp timeout 240

HTH

[Imran Ahmad]

Ok I will to change the value after few hours. as I cannot change at the moment