Folks, I had some very basic questions on the way hashing takes place on Cisco switches connected to each other over a port channel. Considering that 2 links are used between the switch, namely port Gi 0/1 and Gi 0/2. 1) By default I understand that this could be a L2 etherchannel or L3 etherchannel, the default mode of hashing is still the Source and destination MAC id, am I correct? 2) So now if the source IP of 1.1.1.1 needs to reach to 1.1.1.2 how would the hashing calculation take place? Again I understand that this is on the basis of the last 3 bits from the IP address field. 001 and 010 come to 011 which is 3. So based on the number of ports it will select which interface to assign.   I still do not understand what has the below output got to do with the selection:   Core-01#sh interfaces port-channel 40 etherchannel Age of the Port-channel   = 204d:07h:40m:10s Logical slot/port   = 14/3          Number of ports = 2 GC                  = 0x00000000      HotStandBy port = null Passive port list   = Te1/4 Te2/4 Port state          = Port-channel L3-Ag Ag-Inuse Protocol            =    - Port security       = Disabled Fast-switchover     = disabled Fast-switchover Dampening = disabled Load share deferral = disabled Ports in the Port-channel: Index   Load      Port          EC state       No of bits ------+------+------------+------------------+-----------  0      E4            Te1/4                 On   4  1      1B            Te2/4                 On   4 Time since last port bundled:    204d:07h:19m:44s    Te2/4 Time since last port Un-bundled: 204d:07h:19m:54s    Te1/4 Core-01#   What does that load-value mean? and how is that calculated? and does that have a role to play in the selection of the port?     Thanks, Nik   ... View more

Folks, I have attached a topology which we are looking to achieve for some routing design. Below are the questions:   1) We need that the P-2-P link between both the Data Center is used only by the traffic betweens the Data Centers. 2) Consider a scenario that the link between Provider-2 and the Data Center goes down. In this case Branch Office-02 should reach the Data Center via the Backup Data Center --> Provider-1 --> Data Center. What are the option that I can enable this to work?     Thanks, Nik ... View more

Folks, I seen a network with some wired behavior when BGP is enabled with another ISP.   TIll now that network was having BGP enabled with a single Provider(Provider A) who had 2 links coming in and at the back end it was a blended solution, one of those COLO providers kind of setup.   Recently they enabled BGP with a single ISP and seen that some kind of packets drops were being caused.   On one network; e.g. 1.1.1.0 /24 we were trying to ping different hosts from outside. Say 1.1.1.1 and 1.1.1.3 would respond to ping and 1.1.1.5 and 1.1.1.6 would not. In just 30 secs 1.1.1.5 and 1.1.1.6 would respond to ping and 1.1.1.1 and 1.1.1.3 would start giving ping drops. Again 1.1.1.1 and 1.1.1.3 would respond to ping and 1.1.1.5 and 1.1.1.6 would not.   Any suggestion on what to look for? In this case we are not advertising the network 1.1.1.0/24 to the Provider A(i.e. the new provider) for now. Still this network is giving packet drops.   Regards, Nikhil Kulkarni. ... View more

I came across a requirement to achieve some routing preference using BGP with the service provider on the Internet. We are having 2 Internet links from different service providers, Provider-A and Provider-B and both running BGP with us. The BGP is configured to send full routing updates. For a particular network say 1.1.1.0 /24 we want to prefer Provider-A as the preferred provider for incoming and outgoing traffic. How best can this be achieved? For incoming traffic we can simply prepend the network 1.1.1.0 /24 with higher AS path out of Provider-B. Is it a general practice that Provider-B strip the prepends? How can we work on the outgoing traffic? Route-maps?   Thanks, Nik ... View more