Detect High CPU on a Cisco Switch

Recently, I have had an issue on a Core Switch. This switch was running at 80% of CPU for 3 days. The CPU was not monitored and we have not received a syslog message on our server.
Also, I have decided to use the following command (on 4k5) in order to trigger a syslog alert in case of High CPU:

process cpu threshold type total rising 60 interval 20

This command trigger a syslog alert if the CPU exceeds 60 percent for a period of 20 seconds.

EEM - Generate a customized syslog message

In order to generate a customized syslog message, you can use EEM (Embedded Event Manager). This is a Cisco tool. It helps to monitor events and generates an action when an particular event occur. In my case, I would like generate a customized Cisco log message if my primary WAN link is down. This message will have an 'alerts' level with my own description. By default, if an interface goes down it will only generate a 'informational' message. The policy of my syslog server is to generate an email only if I receive an 'error' level message.
I monitor interface giga1/1. If this this interface goes down (log message), I generate my customized message. You can see below the configuration:


event manager applet WanMonitor
 event syslog pattern "Interface GigabitEthernet1/1, changed state to administratively down"
 action 1.0 syslog priority alerts msg "PRIMARY WAN LINK is DOWN on Core 1"

Giant frames on VSL link

I was checking the VSL link on a network and I have found a lot of giant:

show int Te1/5/5TenGigabitEthernet1/5/4 is up, line protocol is up (connected)
       8 runts, 1739095 giants, 0 throttles

I have searched on cisco.com and I have found the following:
The VSL carries data traffic and in-band control traffic between the two chassis. All frames forwarded over the VSL link are encapsulated with a special 32-byte header, which provides information for the VSS to forward the packet on the peer chassis. 

I guess if a packet close to1500 MTU is received and a 32-byte header is added, we have giant packet. If I'm wrong, don't hesitate to correct me.

VPN connexion and Internet Access

When you are connected to a VPN session, normally you can access to the corporate LAN.
However, it's also possible to have access (in the same time) to Internet.

To do this on ASA, you have to configure some NAT rule.
All traffic that will go to Internet have to use the Internet facing interface like source IP address.

The configuration below is an example that can be applied:

ip local pool Pool_VPN 192.168.40.10-192.168.40.250 mask 255.255.255.0

!

interface GigabitEthernet0/1

 description Outside Facing Interface

 nameif INTERNET

 security-level 0

 ip address 199.199.199.199 255.255.255.240

!

object network NAT-VPN-POOL

 subnet 192.168.40.0 255.255.255.0

 description Pool VPN

!

object network NAT-VPN-POOL

 nat (any,INTERNET) dynamic interface

All traffic with VPN IP Pool source address and with Internet destination will match this NAT rule.
Source address will be modified with the outside interface.

Are you impacted by DNS Changer ?

You can test if you are impacted by the virus DNS changer with the web site below:

http://www.dns-ok.ca/

SUP2T and access to CMP

Just a quick post to talk about the SUP2T and the CMP. CMP (Connectivity Management Processor) is an equivalent of the 'aux' port. On our lab we have decided to test this new feature.
But to access to this interface we need an IP address, but which address ? Maybe, there is DHCP server on this interface ?
We have tested and there is nothing. So we have decided looking for on the cisco web site without success. We have just found on a forum someone who has already encountered this issue.
And, the solution to access to the CMP (and configure it) is to use his default IP which is 192.168.1.101/24 (GW 192.168.1.1).
I hope this will help you. And you will not search everywhere on the cisco web site like us.

Good bye ARP, welcome ICMPv6

Today I was working on an IPv6 lab. I wanted discover the relation between an address MAC and an IP address. So, on the windows machine I execute the command 'arp -a'. It's a bad reflex, why ? ARP no longer exists in IPv6. The equivalent is now realized with ICMPv6. So to discover the correlation between MAC and IP address we have to use these commands:

• On a windows laptop:

C:\Users\Administrator>netsh interface ipv6 show neighbors 14

Interface 14: LAB

Internet Address                               Physical Address    Type
--------------------------------------------           -----------------             -----------
fe80::2                                             00-14-1c-c9-d9-a8    Stale (Router)
fe80::214:1cff:fec9:d9a8                     00-14-1c-c9-d9-a8    Stale (Router)
ff02::2                                              33-33-00-00-00-02     Permanent
ff02::5                                              33-33-00-00-00-05     Permanent
ff02::c                                              33-33-00-00-00-0c     Permanent
ff02::16                                            33-33-00-00-00-16     Permanent
ff02::1:2                                           33-33-00-01-00-02     Permanent
ff02::1:3                                           33-33-00-01-00-03     Permanent
ff02::1:ff00:2                                     33-33-ff-00-00-02      Permanent
ff02::1:ff00:d                                     33-33-ff-00-00-0d      Permanent
ff02::1:ff00:f                                      33-33-ff-00-00-0f       Permanent
ff02::1:ff08:c77                                 33-33-ff-08-0c-77       Permanent
ff02::1:ffae:564d                               33-33-ff-ae-56-4d       Permanent
ff02::1:ffc9:d9a8                               33-33-ff-c9-d9-a8       Permanent  
  

• On a Linux laptop (has to be validated):

ip -f inet6 neigh show

• On a Cisco router:

R2#show ipv6 neighbors
IPv6 Address                                         Age Link-layer Addr    State      Interface
FE80::4491:69A9:39F3:7344                   5     000c.2928.4c53  STALE    Fa0/0
2001:DB9:1:1:DD52:657C:D340:F2FF      19   000c.2980.fc6c   STALE    Fa0/0
2001:DB9:1:1:B140:2298:3E92:A99B       6     000c.2928.4c53  STALE    Fa0/0
FE80::1                                                 4     0016.479a.f630   STALE    Fa0/0
FE80::20C:29FF:FE80:FC6C                  19    000c.2980.fc6c   STALE    Fa0/0
2001:DB9:1:1::1                                     22    0016.479a.f630  STALE    Fa0/0