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Beginner

nexus-switches issues no arp-requests.

Hallo all,

I see a very strange behavior on my two nexus switches.

Both are Nexus 5548 with L3-daughter-cards. Both do l2 and l3-switching, ACL-filtering and other things. Furthermore I have a set of servers connected to both switches in a vPC-setup. All in all I do nothing special.

After reloading the primary switch (vpc-primary, root-bridge for all vlans and hsrp-active with preemption for all SVIs) the switche comes back online and after getting up all links and reconverging everthing the network breaks. After a lot of debugging and curses and connection tries and a few additional gray hairs later I have got it to work by pinging all ip-addresses from the switch that I have previously rebooted.

Later I do some tests to find out what was going wrong. I found out that if I clear the arp-cache I will get the same issue. Pinging from server A in one subnet to server B in another subnet doesn't lead to success, because the switch issues no arp-requests. To make it work just ping server B from the switch and all works fine. The switch does arp, the arp-table is updated and the pings from the server A will reach the server B.

Any ideas?

Regards

Thomas

^^°-°^^

3 REPLIES 3
Beginner

nexus-switches issues no arp-requests.

Can you share the config?

Beginner

nexus-switches issues no arp-requests.

I can post a extraction of the relevant config items.

   - --[ vpc-primary

cfs01# sh run

!Command: show running-config

!Time: Wed Nov 13 08:46:18 2013

version 5.2(1)N1(1b)

cfs eth distribute

vrf context CEPH

vrf context management

  ip route 172.31.0.0/20 172.31.8.190

vlan 14

  name 172.31.50.0/26_CN/NN/OSDs@DMZ

vlan 4080

  name 172.31.48.64/26_NAS.Infrastr@DMZ

spanning-tree vlan 1-129,131-3967,4048-4093 priority 0

udld aggressive

vpc domain 1

  role priority 1

  peer-keepalive destination 172.31.8.179 source 172.31.8.178

  peer-config-check-bypass

  delay restore 150

  peer-gateway

  auto-recovery

  ip arp synchronize

interface Vlan14

  no shutdown

  mtu 9216

  description CN/NN/OSDs@DMZ

  ip access-group acl-vl14-in in

  vrf member CEPH

  no ip redirects

  ip address 172.31.50.61/26

  no ip port-unreachable

  hsrp version 2

  hsrp 3

    authentication md5 key-string 3-14

    preempt delay minimum 30 reload 60

    priority 255

    ip 172.31.50.62

interface Vlan4080

  no shutdown

  mtu 9216

  description NAS.Infrastr@DMZ

  ip access-group acl-vl4080-in in

  vrf member CEPH

  no ip redirects

  ip address 172.31.48.125/26

  no ip port-unreachable

  hsrp version 2

  hsrp 3

    authentication md5 key-string 3-4080

    preempt delay minimum 30 reload 60

    priority 255

    ip 172.31.48.126

interface port-channel7

  switchport mode trunk

  switchport trunk native vlan 991

  spanning-tree port type network

  speed 10000

  vpc peer-link

interface port-channel100

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14-19,991,4078-4080

  speed 10000

  vpc 100

interface port-channel102

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14,18,991,1299-1400

  speed 10000

  vpc 102

interface Ethernet1/1

  no cdp enable

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14-19,991,4078-4080

  channel-group 100 mode active

interface Ethernet1/3

  no cdp enable

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14,18,991,1299-1400

  channel-group 102 mode active

interface Ethernet1/29

  description cfs02_Eth29

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface Ethernet1/30

  description cfs02_Eth30

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface Ethernet1/31

  description cfs02_Eth31

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface Ethernet1/32

  description cfs02_Eth32

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface mgmt0

  description oam01_Gi0/19

  ip address 172.31.8.178/26

cfs01#

   - --[ vpc-secondary

cfs02# sh run

!Command: show running-config

!Time: Wed Nov 13 08:46:05 2013

version 5.2(1)N1(1b)

cfs eth distribute

vrf context CEPH

vrf context management

  ip route 172.31.0.0/20 172.31.8.190

vlan 14

  name 172.31.50.0/26_CN/NN/OSDs@DMZ

vlan 4080

  name 172.31.48.64/26_NAS.Infrastr@DMZ

spanning-tree vlan 1-129,131-3967,4048-4093 priority 4096

udld aggressive

vpc domain 1

  role priority 2

  peer-keepalive destination 172.31.8.178 source 172.31.8.179

  peer-config-check-bypass

  delay restore 150

  peer-gateway

  auto-recovery

  ip arp synchronize

interface Vlan14

  no shutdown

  mtu 9216

  description CN/NN/OSDs@DMZ

  ip access-group acl-vl14-in in

  vrf member CEPH

  no ip redirects

  ip address 172.31.50.60/26

  no ip port-unreachable

  hsrp version 2

  hsrp 3

    authentication md5 key-string 3-14

    priority 254

    ip 172.31.50.62

interface Vlan4080

  no shutdown

  mtu 9216

  description NAS.Infrastr@DMZ

  ip access-group acl-vl4080-in in

  vrf member CEPH

  no ip redirects

  ip address 172.31.48.124/26

  no ip port-unreachable

  hsrp version 2

  hsrp 3

    authentication md5 key-string 3-4080

    priority 254

    ip 172.31.48.126

interface port-channel7

  switchport mode trunk

  switchport trunk native vlan 991

  spanning-tree port type network

  speed 10000

  vpc peer-link

interface port-channel100

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14-19,991,4078-4080

  speed 10000

  vpc 100

interface port-channel102

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14,18,991,1299-1400

  speed 10000

  vpc 102

interface Ethernet1/1

  no cdp enable

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14-19,991,4078-4080

  channel-group 100 mode active

interface Ethernet1/3

  no cdp enable

  switchport mode trunk

  switchport trunk native vlan 991

  switchport trunk allowed vlan 2,14,18,991,1299-1400

  channel-group 102 mode active

interface Ethernet1/29

  description cfs01_Eth29

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface Ethernet1/30

  description cfs01_Eth30

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface Ethernet1/31

  description cfs01_Eth31

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface Ethernet1/32

  description cfs01_Eth32

  switchport mode trunk

  switchport trunk native vlan 991

  channel-group 7 mode active

interface mgmt0

  description oam02_Gi0/19

  ip address 172.31.8.179/26

cfs02#

Highlighted
Beginner

nexus-switches issues no arp-requests.

fuck. The faulty behavior disappears. Just rebooting the nexus-switch. Two days to view a lots of logg-messages, error discovery, tests... For what? For nothing. And now I'm not absolutely sure that the fault will not raise up again. That does not inspire me with confidence.

^^°-°^^

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