Overloading NAT with Port Address Translation
As mentioned earlier, NAT is one of the key features that helped to reduce the speed at which the IPv4 address space was being depleted. NAT overloading, also known as Port Address Translation (PAT), is the NAT feature that actually provides the significant savings of IP addresses. The key to understanding how PAT works is to consider the following: From a server’s perspective, there is no significant difference between 100 different TCP connections, each from a different h..
To achieve WFQ’s goals for allocating link bandwidth, WFQ uses a scheduler that is actually pretty simple. The WFQ scheduler takes the packet with the lowest sequence number (SN)(also sometimes called finish time, or FT) when it needs to move the next packet to the hardware queue. WFQ assigns each packet an SN when the packet is added to a WFQ flow queue. The SN assignment process is actually the more interesting part of the scheduler.The WFQ scheduler includes both the p..
Understanding the Detrimental Effects of LDP Restart
At this point, the discussion turns to the issues that arise when the LDP control-plane component of an LSR restarts. As described earlier, an LDP session is established over TCP. When an LDP control-plane component on an LSR restarts, the restarting LSR (on which the control plane has restarted) loses LDP sessions with its LDP peers. RFC 3036 requires that whenever the TCP connection supporting an LDP session fails, LDP must immediately release all FEC-to-label mappings, inc..
Sometimes, the Cisco enable or secret password is unknown and thus you must use password recovery to attain or change the enable or secret password. Password recovery allows the network administrator to recover a lost or unknown password on a Cisco router. For password recovery, an administrator must have physical access to the router through the console or auxiliary port. When an EXEC user enters an incorrect enable password, the user receives an error message similar to th..
You can create a DVMRP tunnel from a Cisco router to a nonCisco DVMRP device by using the special DVMRP tunnel mode. This allows you to pass multicast traffic through a section of network that doesn't support multicast routing: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#ip multicast-routing Router1(config)#interface Tunnel0 Router1(config-if)#ip unnumbered FastEthernet0/0 Router1(config-if)#ip pim spars..
