Sunday, October 31, 2010
Sunday, May 9, 2010
Saturday, May 1, 2010
Friday, April 2, 2010
Master/slave or DR/BDR election:
This is a second election process in OSPF to exchange information without collision in the network.
Parameters for election process are
1. Priority (by default the priority is 1) - first preference.
2. Highest router-id - second preference.
Master/Slave election takes place in point-to-point nature i.e, when routers connected using serial interface.
Master router will collect the information about all the router with a Area, and then it will exchange the information to all other router in the network, thus collision can be avoided. Slave router will also have the same information what master has but it will act as normal router performing its work only.
DR/BDR (Designated Router Back-up Designated Router) election takes place in broadcast nature i.e., when routers connected using Ethernet interface.
Master router will collect the information about all the router with a Area, and then it will exchange the information to all other router in the network, thus collision can be avoided. BDR is a back-up to DR whereas when DR goes down immediately BDR will become DR to continue the process. The remaining router will be DR others by performing their work only.
Wednesday, March 31, 2010
OSPF elections
1. Router ID election
The router ID is used to specify a particular router in a area, which is in ip address format.. the parameter used for router ID election are
a. Manual ID - Statically assigned id.
b. Loopback Address - Dynamically assumed from configuration.
c. Highest Interface
Address - Dynamically assumed from configuration.
In these three parameter's first preference is given to Manual id(if any) else it will check for loopback address(if any) this is second preference else it'll go for last option of choosing highest interface address.
2. Master/slave or DR/BDR election.
OSPF tables
Routing table : Basic table, it holds routing information.
Neighbor table : Maintains information of its neighbor routers.
Database table : Maintains the entire protocol's database information.
Sunday, March 28, 2010
Redistribution:
Redistribution is a process used to make communication between two different routing protocols and also two different Autonomous Systems in IGRP and EIGRP protocol.
Redistribution can be performed in intermediate router only. Intermediate router means "it is a router where two different protocols or two different AS is enabled".
Example for redistribution with different protocols and commands:
Assume RIP and EIGRP is enabled in this router.
router(config)#router rip
router(config-router)#redistribute eigrp 10 metric 5
(The range of metric is 0-16, it is RIP metric). Do you know why metric is specified? we are redistributing EIGRP in RIP, does RIP knows how EIGRP calculates metric? no. that's y metric is specified, whatever metric it receives with EIGRP update will be converted into the metric what is specified.
router(config-router)#exit
router(config)#router eigrp 10
router(config-router)#redistribute rip
(The range of metric is 1- 4294967295, it is EIGRP metric).Do you know why metric is specified? we are redistributing RIP in EIGRP, does EIGRP knows how RIP calculates metric? no. that's y metric is specified, whatever metric it receives with RIP update will be converted into the metric what is specified.
Example for redistribution with different AS and commands:
Assume IGRP 20 and 30 is enabled in this router.
router(config)#router igrp 20
router(config-router)#redistribute igrp 30
Here, it is not necessary to specify the metric, y because both are igrp(same protocol).
router(config-router)#exi
router(config)#router igrp 30
router(config-router)#redistribute igrp 20
Here, it is not necessary to specify the metric, y because both are igrp(same protocol).
What is Autonomous System number?
Autonomous System number is numeric value with the range from 1 to 65535 is used to express a network or a group of network comes under single administration with same routing policy.
IGRP and EIGRP uses AS number, OSPF also uses AS number in the form of Process ID.
In IGRP and EIGRP different AS number will not communicate(exchange update) by default, to make them communicate we need to go for redistribution process.
whereas in OSPF no such issues different AS will communicate by default.
commands:
router(config)#router igrp 10
router(config)#router eigrp 100
router(config)#router ospf 20
Sunday, March 21, 2010
Protocol and standards.
| Protocol | Standard | Developer |
| RIP | Open. | RFC (Request For Comment), 1988. |
| IGRP | Only for CISCO routers. | CISCO, Mid-1980’s. |
| EIGRP | Only for CISCO routers | CISCO. |
| OSPF | Open. | RFC 2328, 1998. |
| IS-IS | Only for defense department. | OSI. |
| BGP | Open. | CISCO, RFC, 1990’s. |
Sunday, March 7, 2010
What is ICMP Protocol?
ICMP - Internet Control Message Protocol
ICMP is a control protocol, meaning that it does not carry application data, but rather information about the status of the network itself. ICMP can be used to report.
· errors in the underlying communications of network applications.
· availability of remote hosts.
· network congestion.
What is RARP?
RARP – Reverse Address Resolution Protocol.
The RARP protocol is used to find the unknown IP address for the Known MAC(Media Access Control)address.
What is ARP?
ARP – Address Resolution Protocol.
The ARP protocol is used to find the unknown MAC(Media Access Control) address for the Known IP address.
Protocol and Port Number:
| TCP | UDP |
| FTP 20, 21 | DNS 53 |
| TELNET 23 | TFTP 69 |
| SMTP 25 | SNMP 161 |
| HTTP 80 | |
| HTTPS 443 | |
| | |
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