Skip to main content

Simplified OSPF TTL Security: A Key Layer of Network Protection

OSPF TTL Security is a feature used to enhance the security of OSPF routing by limiting the range of OSPF packets to prevent them from being spoofed by unauthorized devices that are not directly connected. It ensures that OSPF packets received by a router are from legitimate neighbors within a specific TTL (Time To Live) range.

How OSPF TTL Security Works:

  1. TTL Field: Every IP packet has a TTL field, which is decremented by 1 at every hop. When the TTL reaches zero, the packet is discarded.
  2. Default TTL: By default, OSPF packets have a TTL value of 255 when sent from a router.
  3. TTL Check: In OSPF TTL Security, the receiving router checks the TTL value of incoming OSPF packets. If the TTL is less than the specified threshold, the packet is discarded.
  4. Security Mechanism: The TTL security feature is particularly useful in preventing OSPF adjacency formation with routers that are multiple hops away. It ensures that only directly connected OSPF neighbors can establish adjacency, which helps prevent unauthorized or malicious OSPF packets from influencing the network.

Configuration Example:

To enable TTL security, you can configure a router to accept OSPF packets only if they arrive with a TTL value of 254 or higher (indicating that the OSPF router is one hop away):

router ospf 1

 ttl-security all-interfaces hop-count 1

  • hop-count 1 ensures that OSPF neighbors must be directly connected, as TTL must be 255 when the packet is sent and 254 when received.

Benefits:

  • Prevents Spoofing: Reduces the risk of attackers injecting malicious OSPF packets from remote locations.
  • Simple Implementation: Easy to implement on existing OSPF networks without significant configuration changes.
Labels:

Comments

Post a Comment

Popular posts from this blog

How to import Putty Saved Connections to mRemoteNG

Just started using mRemoteNG and its being very cool to connect to different remote connection with different protocols e.g Window Remote Desktop, VNC to Linux, SSH, HTTP connection etc. from a single application. As new user I configured some remote desktop connection which was quite easy to figure out. But when I wanted to add SSH connections, it came in my mind to import all of the saved connections in the putty. But I couldn't figure it out how can it be done, though it was quite easy and here are the steps. Open your mRemoteNG Create a folder if you want segregation of multiple networks Create a new connection Enter the IP address of remote server under connection in Config pane Under the config pane, select protocol " SSH version 2 ".  Once you select protocol to SSH version 2 you are given option to import putty sessions, as shown in the snap below. In the above snap, I have imported CSR-AWS session from my saved sessions in Putty.
1 comment
Read more

BGP Local Preference Controlling Outbound Traffic in BGP

In BGP, Local Preference is used to control the outbound traffic path. It helps you decide which egress point (exit point) should be used when you have multiple connections to external networks, such as ISPs. Local Preference is an attribute that is local to your AS and is shared with all iBGP peers but not with eBGP neighbors. Higher Local Preference = More preferred outbound path. Example Scenario : You have two external links: ISP1 (via CE1) and ISP2 (via CE2). You want traffic to prefer ISP1 for all outbound traffic. Network Topology : CE1 (connected to ISP1): 10.0.1.1/30 CE2 (connected to ISP2): 10.0.2.1/30 iBGP Router (Internal) connected to both CE1 (10.0.1.2/30) and CE2 (10.0.2.2/30). Configuration on CE1 (Higher Local Preference) : Create a route map to set the local preference to 200 for routes learned from CE1: route-map SET_LOCAL_PREF permit 10 set local-preference 200 In the BGP configuration for CE1, apply this route map to the neighbor: router bgp 65001 ne...
Post a Comment
Read more

AS Path Prepending: Controlling Inbound Traffic in BGP

AS Path Prepending is a BGP feature used to make a specific path appear less preferred by artificially lengthening the AS path. This is done by adding your AS number multiple times to the AS path. It is a common method to influence inbound traffic from external networks. Longer AS Path = Less preferred route . Example Scenario : You have two ISPs: ISP1 (through CE1) and ISP2 (through CE2). You want inbound traffic from the internet to prefer ISP1 over ISP2. Network Topology : CE1 (connected to ISP1): 10.0.1.1/30 CE2 (connected to ISP2): 10.0.2.1/30 iBGP Router (Internal) connected to both CE1 (10.0.1.2/30) and CE2 (10.0.2.2/30). Configuration on CE2 (AS Path Prepending to Make ISP2 Less Preferred) : Create a route map to prepend your AS path multiple times for CE2: route-map PREPEND_AS permit 10 set as-path prepend 65001 65001 65001 Apply this route map to the neighbor in the BGP configuration for CE2: router bgp 65001 neighbor 10.0.2.1 remote-as 65002 neighbor 10.0.2.1 ro...
Post a Comment
Read more