Search

Language:  
Search for:

Available article translations:

Overflowing ARP table in VM with network in routed mode

Article ID: 117015, created on Aug 29, 2013, last review on Aug 12, 2014

APPLIES TO:
  • Virtuozzo
  • Virtuozzo hypervisor

Symptoms

Virtual Machine with CentOS/Redhat can experience ARP (neighbour) table overflow.

This can happen when Parallels Tools are installed in VM, the network interface is configured in the routed mode:

~# prlctl list VM_Name -i | egrep '^Guest|^  net[0-9]'
GuestTools: state=installed version=7.0.13392.803029
  net0 (+) dev='vme58a0a9f1.0' type=routed mac=001C42xxxxxx card=rtl ips='192.168.86.124/255.255.255.255 ' gw='192.168.86.1' 
~#

The log file /var/log/messages in VM contains records like these:

Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:38 collector01 kernel: Neighbour table overflow.
Aug  7 15:49:43 collector01 kernel: __ratelimit: 3769 callbacks suppressed

Cause

The issue occurs because the default gateway in VM is configured with scope host instead of scope link.

~# ip route
169.255.30.1 dev eth0  scope host 
169.254.0.0/16 dev eth0  scope link  metric 1002 
default via 169.255.30.1 dev eth0 
~# ip route get 8.8.8.8
8.8.8.8 dev eth0  src 192.168.86.124 
    cache  mtu 1500 advmss 1460 hoplimit 64
~# 

Since eth0 is the Ethernet interface, ARP-capable - this means that ARP resolution should be used for communication with remote hosts and the kernel stores ARP record for external IPs with the MAC address of the host server.

Whereas the expected output should be:

~# ip route get 8.8.8.8
8.8.8.8 via 169.255.30.1 dev eth0  src 192.168.86.124 
    cache  mtu 1500 advmss 1460 hoplimit 64
~# 

Resolution

The fix is included in Parallels Server Bare Metal 5 update 10 and in Parallels Cloud Server 6.0 update 4, installing updates is the recommended solution.

If installing updates is not an option, the patch can be applied.

To correct the behaviour, the proper scope link should be configured. The configuration is set by the scripts installed in VM with Parallels Tools:

/usr/lib/parallels-tools/tools/scripts/redhat-set_gateway.sh
/usr/lib/parallels-tools/tools/scripts/redhat-set_route.sh

So, to resolve this issue please follow the steps:

  1. Download attached patch on your server to /root/ directory.

  2. Implement it:

    ~# (cd /usr/lib/parallels-tools/tools/scripts/; patch -p1 -i /root/scope.patch)
    
  3. restart VM or suspend/resume it or reapply network settings.

Attachments

scope.patch

Search words:

PSBM-21740

virtual machine

ARP table overflow

PSBM-21739




a26b38f94253cdfbf1028d72cf3a498b 2897d76d56d2010f4e3a28f864d69223 0dd5b9380c7d4884d77587f3eb0fa8ef

FEEDBACK
Was this article helpful?
Tell us how we may improve it.
Yes No
 
 
 
 
 
 
Server Virtualization
- Odin Cloud Server
- Odin Containers for Windows 6.0
- Odin Virtuozzo Containers
Automation
- Odin Automation
- Odin Automation for Cloud Infrastructure
- Odin Business Automation Standard
- Odin Virtual Automation
- Odin Plesk Panel Suite
- Web Presence Builder
- Odin Plesk Automation
- Odin Small Business Panel
- Value-added Services for Hosters
- Odin Partner Storefront
Services & Resources
- Cloud Acceleration Services
- Professional Services
- Support Services
- Training & Certification