Tag: link

Link Aggregation (LAG) Port (EtherChannel – Cisco)

by Samuel Mitchell, posted in Cisco, Routing & Switching

In the field of networking, there is a concept called Link Aggregation (LAG) which is a technology of combining more than one physical link together to make one logical link. This technology is usually implemented to support link redundancy and in some case higher throughput depending on the vendor. This technology is used mostly to connect servers to switches with multiple network cards. LAG ports are mostly connected in pairs of 2 e.g. 4, 8.

in this article, we are going to focus on the vendor Cisco who calls this technology by a different name, “Etherchannel”.

There are two protocols used on the Cisco switches to support Etherchannel:

  • LACP – Link Aggregation Control Protocol (Cisco proprietary)
  • PAgP – Port Aggregation Protocol (IEEE standard)

LACP protocol

  • Active
  • Passive

PAgP protocol

  • Auto
  • Desirable

Manual – On

Etherchannel configuration

switch(config-if-range)# channel-protocol [lacp/pagp]

switch(config-if-range)# channel-group # mode [protocol]

Etherchannel load-balance

  • src-mac (default)
  • dst-mac
  • src-ip
  • dst-ip
  • src-dst-mac
  • src-dst-ip

Loadbalance configuration

switch(config)# port-channel loadbalance [balance-option]

Layer 3 Etherchannel

an Etherchannel port become layer 3 (routing) port once your disable switchport on the portchannel

switch(config)# interface port-channel 1

switch(config-if)# no switchport

Show summary of the etherchannel

Tips:

  • Configurations applied to the port-channel interface is also applied to all the physical interfaces assigned to the port-channel group.
  • Layer 3 EtherChannel interface is not allowed on LAN based switches.
  • The following ethernet port settings must be the same when configuring the EtherChannel:
    • Speed
    • Duplex
    • native VLAN
    • VLAN range
    • trunking status
    • trunking type
  • When configuring the EtherChannel modes, one side must be in an active negotiating state (Desirable or Active)
  • Maximum interface support in one etherchannel is 8 and the maximum portchannel support on a switch is 64 depending on the switch model.
  • PAgP not supported on cross stack switches.

 

Almost caught by Spam

by Samuel Mitchell, posted in Exchange, Security, Uncategorized

I had receive the following spam email which seems to come from Paypal:

Spam_email_paypalMarch132018_edit

At first glance, it looks very legitimate but after close inspection, it was discovered to be a spam. This provides the opportunity to highlight some indications that the email received is a spam and how to mitigate against it.

  • Check the email address that it is coming from. Not the one that is displayed at first glance but when it is opened, the email address that is between these symbols <>. In the example above, it says it is coming from service@paypal-int.co.uk. (Paypal correct address is service@intl.paypal.com).

 

  • Check where the link that you are asked to click on is point to by just hovering the mouse pointer over the hyperlink and look at the bottom of the browser. The spam email said the following:

    If you did not initiate this payment, we recommend that you go to Manage/Cancel Payment

    The Manage/Cancel payment was pointing to an unknown URL and not to the Paypal website so you know that it is a malicious website it is asking you to click on.

 

  • Usually the greeting will include the email address it is sent to. In this case, I was address by my email address (*****@gmail.com) and not by my full name which the Paypal will have on record.

Now for those who are unsure if this event actually happened that the email is stating. Verify the transaction by logging on directly to your website or portal (not using the email links) in my case Paypal.com and check if any such event has occurred.

I hope this is helpful and don’t be fooled by well crafted spam emails.

Keep safe…Keep secure