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What will happen if a router received a ICMP packet with TTL 0?
1.The router will discard the packet. 2.The router will send a time exceeded message to the source host.
How TTL is operating?
TTL (Time to Live) is reduced by 1 every time a router forwards the packet. The purpose of this is to reduce the negative effects of routing loops. If two routers are misconfigured (it happens) and send a packet back and forth to each other assuming the other router will take care of it, the packet would simply never go away, if it wasn't for TTL. It guarantees that this can only happen a maximum of 256 times (generally quite a bit less). Once that TTL reaches zero, the packet is discarded.
What does the TTLvalue zero indicate?
The TTL (Time To Live) value is a number associated with network routing packets. An information packet will only be forwarded to a certain number of routers before the packet is dropped (deleted). The TTL is a counter decreased by 1 when the packet is forwarded to another router. When the TTL reaches zero, it will not be forwarded to another router.
Can you explain the concept of TTL?
Time-to-Live (TTL) is a value in an Internet Protocol (IP) packet that tells a network router whether or not the packet has been in the network too long and should be discarded.
Which field of ip address is changes from router to router?
The TTL will be reduced by one every time it passes a router. Because this changes the IP header, the checksum also has to be recalculated.The TTL will be reduced by one every time it passes a router. Because this changes the IP header, the checksum also has to be recalculated.The TTL will be reduced by one every time it passes a router. Because this changes the IP header, the checksum also has to be recalculated.The TTL will be reduced by one every time it passes a router. Because this changes the IP header, the checksum also has to be recalculated.
How important is TTL to network security what is TTL for and can a Hacker use it to harm you PC or network?
TTL stands for "Time To Live". This is a piece of data in a network packet that specifies how many routers the packet can pass through before the packet expires and is thrown away. Every router that the packet travels through subtracts one from the TTL counter. When it reaches zero, the packet expires. The router will drop the packet, and then send a message back to the computer that sent the packet telling it that the packet has expired. The purpose of the TTL counter is to make routing loops less dangerous. Let me explain.... Routers are devices that look at an incoming data packet and decide where to send it to get it one step closer to its destination. It's possible for one or more routers to be configured such that router A sends the packet to router B, which sends it to router C, which sends it to router A, which then starts it over again. Without the TTL counter, this packet (and any subsequent packet sent to the same destination) would circulate endlessly, taking up bandwidth until someone fixes the routing loop. However, with TTL, each router subtracts one from the TTL counter until eventually the counter hits zero and the packet goes away, giving someone time to fix the problem before the links are so congested with looping packets that it's no longer possible to talk to the router. TTL can affect network security in a couple of ways. Most operating systems set the TTL counter to 64 or 128, which is a pretty large number that will guarantee your packet can get across the Internet. To improve your network security, you can set your TTL counter to a low number. If your internal network is only four routers wide, you can set your TTL to 4. This will ensure that any packets generated on your network will not travel very far beyond your internal network. An attacker can also use the TTL feature to probe your network for the existence and address of your routers. This feature is used by the "traceroute" or "tracert" utility. It works by sending out a packet with a TTL of 1. The first router that the packet encounters will decrement the TTL to 0, drop the packet, then send a message to the traceroute program telling it that the packet expired. By looking at the source address of this packet, traceroute knows the address of the first router. Next traceroute sends a packet with a TTL of 2, which causes the packet to expire at the second router, which sends a message back to traceroute and exposing its address. And so on. Once an attacker knows the addresses of your routers, he or she can start working on compromising them, which can cause you no end of security problems. The solution is to prevent these packets from reaching your routers by using a firewall to block them. HTH, Gdunge
What is the purpose of TTL field in ip header?
It's a time-to-live field designating that the packet is OK to forward from one device to another for a certain amount of time. If the packet gets caught in a routing loop, it won't just go back and forth forever. If that were allowed to happen, many other packets would be doing the same thing, just being mis-routed back and forth between the confused devices, until the available bandwidth on the link was saturated. The TTL assures that the packet will not be forwarded by the very next routing device that reads the packet's TTL field and sees that its TTL has expired. The packet would be discarded at that point.
Why the ttl change in the same ping?
The TTL (Time to Live) value in a ping packet decreases by 1 each time it passes through a router. This helps prevent packets from circulating endlessly in a network. When a TTL reaches 0, the router discards the packet and sends an ICMP Time Exceeded message.
What are two things will happen if a router receives an icmp packet which has a ttl value of 1 and the destination host is several hops away?
1.The router will discard the packet. 2.The router will send a time exceeded message to the source host.
What happens to an IP datagram when its TTL reaches 0?
what happens to a packet if the TTL field reaches 0 I dont believe a datagram reaches O because once the datagram reaches 1 the router or device discards it.I banged ur mom she sucked this stick B-----D
What is the TTL - Time to Live and Why is it required?
TTL is a value in data packet of Internet Protocol. It communicates to the network router whether or not the packet should be in the network for too long or discarded. Usually, data packets might not be transmitted to their intended destination within a stipulated period of time. The TTL value is set by a system default value which is an 8-bit binary digit field in the header of the packet. The purpose of TTL is, it would specify certain time limit in seconds, for transmitting the packet header. When the time is exhausted, the packet would be discarded. Each router receives the subtracts count, when the packet is discarded, and when it becomes zero, the router detects the discarded packets and sends a message, Internet Control Message Protocol message back to the originating host.
What steps are taken when forwadin an icmp packet?
For each router, the following steps occur: 1) The "access-group in" command is checked on the interface, and discards the packet if the rule tells it to do so. 2) The "TTL" field is decreased by 1. 3) If TTL is now 0, the router discards the packet and sends a reply packet back to the sender. 4) The packet's IP address is compared to the routing table to determine the next hop of the packet. 5) The router advises if the network or host is unreachable due to a down interface or no known route. 6) The router sends the packet to the outgoing interface's queue to be sent to the next hop. 7) The "access-group out" command is checked on the interface, and discards the packet if the rule tells it to do so. 8) The router sends the packet to the next hop.
