Skip to main content

BGP Communities


  • BGP communities are optional transitive attributes
  • They are used mainly to associate an administrative tag to a BGP route
  • In spite of the communities being transitive, Cisco IOS routers do not pass them across the BGP sessions by default. The feature needs to be activated using the command “neighbor send-community”
  • To display the community in the structured notation, you need to enter the global configuration command “ip bgp-community new-format”
  • In order to set a community value, use the route-map command “ set community etc” or to add the community value on the existing community values use “set community additive ”
  • The routes with communities assigned to them can be matched using “community-list” and which can then be referenced in a route-map later. There are two types of community lists : standard and extended. For eg.
  • ip community-list 1 permit 101:1 101:2
  • ip community list 1 deny no-export Std community list
  • NO-ADVERTISE community attribute: The well-known NO_ADVERTISE BGP community signals BGP router not to advertise the particular prefix to any BGP peer.
  • NO_EXPORT community attribute: The well-known NO_EXPORT community instructs the BGP router to advertise the prefix only across iBGP peering links. It ensures that the prefix is not advertised anywhere outside its AS

Labels:

Comments

Post a Comment

Popular posts from this blog

Alibaba Cloud Networking Services List

Virtual Private Cloud - Isolated tenant containing IP address range, network segment, route tables and gateway. NAT Gateway - Allows Alibaba ECS instances to be source NAT'd with public IP to communicate on Internet. Cloud Enterprise Network VPN Gateway Express Connect Smart Access Gateway Alibaba Cloud PrivateZone PrivateLink Network Intelligence Services (NIS) Global Traffic Manager CDN and Edge Alibaba Cloud CDN Secure Content Delivery Dynamic CDN Edge Node Service (ENS) Global Accelerator
Post a Comment
Read more

MITRE ATT&CK - Kerberos Vulnerabilities and Security

From the previous post, the summary of Kerberos authentication process is as below: For the initial authentication, the user’s client machine sends a request to the KDC  Authentication Service (AS) . The request includes details like the user’s username, and the date and time. All information except the username is encrypted using the hash of the user’s password. The KDC AS uses the username to look up its copy of the user’s password hash and uses it to decrypt the rest of the request. If the decryption is successful, that means the client used the correct password hash and the user has successfully authenticated. Once the user is authenticated, the KDC AS sends the user’s client a  ticket granting ticket   (TGT) . The TGT includes a unique session key and a timestamp that specifies how long that session is valid (normally 8 or 10 hours). Importantly, before sending the TGT, the KDC encrypts it using the password hash for a special account, the  KRBTGT account. ...
7 comments
Read more

Checkpoint - Exporting Objects in CSV format

Be it a Network Operations Manager, Security Architect or a Security Auditor, the people up the hierarchy always harangue the Security Engineers to compile the list of firewall objects or rules or policies or the traffic statistics and so on.. This can turn out to be quite hectic especially if there are no built in features to systematically provide the output in a "layman-readable" format. Come, Checkpoint's "Object Explorer..."  which not only provides the output in the "layman-readable" format, but also provides in-built filtering mechanisms, thereby ensuring that the Security Engineer doesn't have to rely on Google for building his scarce Microsoft Excel data filtering skills. The following screenshots will show how easy it is, with Checkpoint R80.10 to generate the firewall configuration inventory. On the SmartConsole Unified Portal, navigate to Menu >> Open Object Explorer... Select the Categories you wish to see in your output: Click o...
Post a Comment
Read more