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When a packet traverses a network each router is a...?
hop
When forwarding a packet which route will the packet select?
First, routing is the process a router performs when making forwarding decisions for each packet arriving at the gateway interface. To forward a packet to a destination network, the router requires a route to that network. If a route to a destination network does not exist on the router, the packet will be forwarded to the default gateway. Now, the destination network can be a number of routers or hops away from the default gateway. If the router has an entry for the network in its routing table, it would only indicate the next-hop router to which the packet is to be forwarded to and not the exact route to the final router. To sum it up, the routing process uses a routing table to map the destination address to the next hop and then forwards the packet to the next-hop address.
When forwarding a route which route will router select?
First, routing is the process a router performs when making forwarding decisions for each packet arriving at the gateway interface. To forward a packet to a destination network, the router requires a route to that network. If a route to a destination network does not exist on the router, the packet will be forwarded to the default gateway. Now, the destination network can be a number of routers or hops away from the default gateway. If the router has an entry for the network in its routing table, it would only indicate the next-hop router to which the packet is to be forwarded to and not the exact route to the final router. To sum it up, the routing process uses a routing table to map the destination address to the next hop and then forwards the packet to the next-hop address.
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.
What information does the next hop entry in a routing table identify?
The first router in the path to the destination network. The next hop router is the first (or next) router in the path to the destination network. Each router looks at the destination network in the packet, then consults the routing table to identify the next hop router to the destination network. The hop count identifies the numbers of routers in the path to the destination network. A default gateway router is a router that is used for packets used to external networks. Most routers do not have a default gateway setting, but instead use a default route setting which identifies the next hop router for all unknown networks.
What packet is a form of protection for your computer that looks at each packet that comes into your computer network?
Screening
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.
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 topology connects each network device to a router?
the don
What does the NAT table do?
NAT - Network Address TranslationNAT is one of the basic fundamental functions of a router. If you want to share your Internet connection with more than one device, you have to use a router (most Internet Service Providers will supply one to you as part of their package). The router acts as your gateway to Internet, taking complete control of your public IP address (the one assigned to you by your ISP) and assigns private IP addresses to all the devices connected to the router (your computers, your mobile phones, your network printers, etc). Those devices are essentially invisible to the Internet; only the router is exposed.NAT is essential whenever two separate networks (such as your private home network and the public Internet) require access to each other but their IP address ranges are incompatible with each other. This is the case with all private networks as they all share a common range of IP addresses. In order to route calls from one network to the other, your router uses two IP addresses -- one outward-facing (public) and one inward-facing (private). Your router than acts as the network's gateway to the Internet and effectively hides your private network from the Internet.When a device sends a request for information from another device on the network, the source device will send a datagram containing the request, along with its own private return address and the address of the device that has the information (all wrapped up in a data packet), which is then forwarded to the router. If the device that has the information is on the same network (such as any device on your home network), then the packet is routed directly to that device without using NAT. However if the device is on another network (such as the Internet), then the router uses NAT to replace the private IP address in the packet with the router's public IP address, and forwards the packet to your service provider. When the requested information comes back from the service provider (usually as a series of data packets), NAT replaces the public IP address in each returned packet with the private IP address of the original device, and forwards the packets to that device.All of this is achieved by maintaining a NAT table, so the router knows where each packet returned from the service provider is intended to be sent, based upon the data packets it initially received and stored in the table. When multiple computers make similar requests at the same time (as is possible), the router must provide some means of differentiating between those requests. Often this will mean altering the port numbers or adding an anonymous token into the packet to ensure every packet is unambiguously identified.Example:You want to look at the wiki answers webpage. Your computer sends a data packet to the router containing its own private IP address, the address of the webserver (which it gets from the Domain Name Server provided by your ISP) and the datagram that describes the request for information. The router looks at the data packet and sees that your computer is requesting information from another network (the Internet), changes the IP address from the private IP address to the public IP address, updates the NAT table accordingly and then forwards the packet to the service provider who will then route it to the webserver. Now the webserver knows where to send the requested information to (your router, via your service provider). When your router receives the requested information from your service provider, it uses the information it stored in the NAT table to restore the original private IP address and then forwards the packet to your computer. There may be more than one packet returned to your computer but the end result is the webpage you requested is displayed in your browser, just as if wiki answers were part of your own private network.
How does the network layer in a connection-oriented packet-switching network differ from the network layer in a connectionless packet switching network?
An upper-layer packet is split into 10 frames, each of which has an 80 percent chance of arriving undamaged. If no error control is done by the data link protocol, how many times must the message be sent on average to get the entire thing through? An connection-oriented service (like TCP) does error checking and requests data to be resend. The packet has several options for error free transport. Connectionless service (think UDP) does not check for undamaged arival. It has a much smaller packet size and is also faster.
