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Internet Protocol, Transport Control Protocol, Network protocols, Routing, Routers, IP aliases, Routes, Ethernet

 [ Total topics 58 Go to page 1, 2, 3, 4, 5, 6

Message
 Post subject: How to generate GRATUITOUS ARP REQUEST on FreeBSD using nemesis packet crafting tool
PostPosted: Thu Feb 23, 2012 4:49 am 
Before going deeper into gratuitous arp, I will introduce "nemesis".

NEMESIS is a command line packet crafting tool able to generate l2 frames / ip packets giving one the possibility to manipulate the arp/ip/tcp/icmp headers.

One and the only disadvantage I see is that it cannot close tcp handshakes (as far as I can see), but it is not the purpose of this article.

Gratuitous arp is a simple mechanism used for different reasons, but ...

Read more : How to generate GRATUITOUS ARP REQUEST on FreeBSD using nemesis packet crafting tool | Views : 2520 | Replies : 0

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 Post subject: Quagga ospf neighbour stuck in ExStart/DROther state
PostPosted: Mon Dec 12, 2011 4:12 pm 
After setting up ospf over gre over ipsec, I noticed that the neighbours were stuck in "ExStart/DROther" state. This was because I adjusted the MTU only on one tunnel end-point (MTU adjustment is necessary for GRE and IPsec encapsulation).
Code:
quagga-router# sh ip ospf neighbor 

    Neighbor ID Pri State           Dead Time Address         Interface            RXmtL RqstL DBsmL
172.16.0.34     128 Full/DROther       5.573s 172.16.0.41     tun0:172.16.0.42         0     0     0
172.16.0.5        1 ExStart/DROther    4.140s 172.16.0.45     tun1:172.16.0.46         0     0     0


Setting ...

Read more : Quagga ospf neighbour stuck in ExStart/DROther state | Views : 1590 | Replies : 0

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 Post subject: How to add IP alias in Debian Linux to last after reboot
PostPosted: Mon Dec 05, 2011 7:38 am 
To add and ip alias in Debian to survive a reboot, edit the file "/etc/network/interfaces" and create a subinterface for ethX and set it's ip address:
Code:
iface eth3:0 inet static
        address 10.0.0.23
        netmask 255.255.255.240
        network 10.0.0.16
        broadcast 10.0.0.31


As soon as the device is rebooted or the network service restarted, this change will take effect. To add the alias immediately without restart, you can use ip command:
user~ sudo ip a add 10.1.1.23/28 ...

Read more : How to add IP alias in Debian Linux to last after reboot | Views : 1733 | Replies : 3

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 Post subject: Linux How to change hardware MAC address of an interface
PostPosted: Sat Dec 03, 2011 9:18 pm 
The mac address is also referred to as physical address and it is used in Ethernet network via ARP and DHCP to map a layer 3 IPv4 address.

Change interface mac address in Linux


To change the mac address of an interface in Linux, the interface needs to be brought down first, otherwise a "device or resource busy" error will occur. This can be done if logged in via ssh to an interface not serving ...

Read more : Linux How to change hardware MAC address of an interface | Views : 1106 | Replies : 1

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 Post subject: FreeBSD PF supported icmp types
PostPosted: Fri Jan 28, 2011 9:15 am 
Here are the ICMP types supported by FreeBSD / OpenBSD PF firewall:

Here is the pf.conf syntax for allowing icmp packets:
Code:
icmp_types="{ echoreq, unreach}"
pass in log on $ext_if1 inet proto icmp from any to $dmz_net icmp-type $icmp_types keep state #queue icmp

And below is a list of supported icmp types:
Quote:
"net-unr",
"host-unr",
"proto-unr",
"port-unr",
"needfrag",
"srcfail",
"net-unk",
"host-unk",
"isolate",
"net-prohib",
"host-prohib",
"net-tos",
"host-tos",
"filter-prohib",
"host-preced",
"cutoff-preced",
"redir-net",
"redir-host",
"redir-tos-net",
"redir-tos-host",
"normal-adv", ...

Read more : FreeBSD PF supported icmp types | Views : 1359 | Replies : 0

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 Post subject: How Does OSPF Neighbor State Change
PostPosted: Thu Jan 20, 2011 4:53 am 
Q1. What are OSPF packets? What do they do?
Answer: There are 5 OSPF packets:
Hello: Discover neighbors.
DD (Data Description): Exchange LSDB catalog (LSA headers).
Request: Ask neighbor to send LSA that I don't have.
Update: Send LSA requested by neighbors.
Ack: Tell Update sending router that I have received your Update.
Q2: What are neighbor states? What do they do?
Answer: There are 7 states:
Down. Neighbor is gone. E.g. neighbor is down, ...

Read more : How Does OSPF Neighbor State Change | Views : 843 | Replies : 1

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 Post subject: OSPF Simulation Tutorial for Beginners (Interactive, Visual)
PostPosted: Thu Jan 20, 2011 4:51 am 
OSPF is a complex protocol. To help beginners grasp abstract its concepts, a different approach is taken -- Visualizing OSPF simulation. This tutorial, OSPF basic, simulates the basic OSPF activities on a simple topology: H1-R1-R2-H2. R1 and R2 are routers. H1 and H2 are hosts. This simulation shows 4 stages:
1) R1 and R2 are not running OSPF. H1 ping H2. It fails.
2) Start OSPF on two routers. R1 and R2 discover each other ...

Read more : OSPF Simulation Tutorial for Beginners (Interactive, Visual) | Views : 557 | Replies : 0

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 Post subject: "OSPF not enabled on this interface" FreeBSD Quagga ospfd interface status
PostPosted: Thu Apr 01, 2010 5:53 am 
While trying to configuring ospf on a FreeBSD Quagga installed server, I couldn't get ospf to use any of the interfaces.

For all of them, "sh ip ospf int" showed OSPF not enabled on this interface:
test_ospf# sh ip ospf interface
em0 is up
ifindex 3, MTU 1500 bytes, BW 0 Kbit <UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>
OSPF not enabled on this interface
gre0 is up
ifindex 5, MTU 1476 bytes, BW 0 Kbit <UP,POINTOPOINT,RUNNING,LINK0,LINK1,MULTICAST>
OSPF not enabled on ...

Read more : "OSPF not enabled on this interface" FreeBSD Quagga ospfd interface status | Views : 2855 | Replies : 1

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 [ Total topics 58 Go to page 1, 2, 3, 4, 5, 6


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