BGP Tips

• Links:

BGP Basics

BGP Attributes

Route Reflector

IGMP Multipath Load Shating

Cisco Q&A





• BGP route selection algorithm

•Weight - Cisco Specific - Not advertised to neighbor routers - Two links to one router both advertising the same network - Higher weight is applied to one and installed into the IP routing table

•Local preference - Two routers receiving updates from a neighbor for the same network - the higher local preference value wins

•Multi-exit discriminator - (MED) suggestion to an external AS for the preferred route - Lower value metric wins - MED's are advertised throughout the local AS

•Origin - How did BGP learn about the route - Three Possible ways -

1.IGP Interior to the originating AS (IGP) Value set when the command was used to inject the route into BGP
2. EGP The route was learned via an Exterior Border Gateway Protocol (EGBP)
3. Incomplete The origin of the route is unknown or learned in some other way. Redistributed into BGP

•AS_path - Shorter AS path wins - updates with the router's own AS are rejected

•Next hop - The IP address that is used to reach the advertising router. For EBGP peers the IP is the connection between the peers - in IBGP the EBGP next hop address is preserved in the local AS.

•Community - Route maps are used to group destinations into a community - Predefined communities are:
no-export - do not advertise this route to EBGP peers
no-advertise - do not advertise this route to any peer
internet - advertise this route to the internet all routers in the network belong to is

• BGP Valid AS Numbers
1 to 64,511
64,512 to 65,535 are reserved fr private use

• In order for two BGP peers to form a BGP session they must first have an active TCP session and be able to reach one another over TCP port 179.

• Alias Commands:
alias exec cib clear ip bgp *
alias sb show ip bgp summary


• Show Commands:
show proc cpu | include BGP
show ip bgp (*> noting best reachable route)
show ip bgp | exclude [AS#]
show run | begin router bgp
show ip bgp neighbors

File Permissions

To add write permission for the group on a file called "file1":

type: chmod g+w file1

To remove read and write permission for the group and others on "file1":

type: chmod go-rw file1

To make "file1" and "file2" executable for yourself:

type: chmod u+x file1 file2

To deny the group and others cd permission to the directory "direct1":

type: chmod go-x direct1

To do several steps at once:

Remove read and write permission on file1 for others, add write permission for the group:

type: chmod g+w,o-rw file1

UNIX Tips and Tricks

First off I want to say that these commands are specific to the mac and should be used to get things like system information and move/open files.

• Secure Copy

From source to Destination

scp /directory/localfile user@hostname.domain.com:filename

- or -

scp local_file user@hostip:/directory/directory/filename

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• Copy via ftp
Say you want to copy an IOS image from a server to a router and tftp keeps timing out.  You can use ftp to perform the task with no issue. You will need to turn on your ftp service and then put the file in your Public directory for the router to access it.  Here is the command:

copy ftp://un:pw@hostname/Public/biglong_imagename(withlots of numbers).bin disk1: 

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• Make a copy of a directory in a new location with ditto:

- Existing directory named bgp, full of files. You want an exact copy of that directory and all the files in it just with a new name:

sudo ditto bgp rip

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• Listing the ports you have configured in your System Preferences/Network

- Enter

networksetup -listallnetworkservices

Built-in Ethernet
PCI Ethernet Slot 3, Port 1
PCI Ethernet Slot 3, Port 2
PCI Ethernet Slot 3, Port 3
PCI Ethernet Slot 3, Port 4
Built-in FireWire
VPN (L2TP)
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• Specific Interface information:

- Enter

networksetup -getinfo "Built-in Ethernet"

- or -

networksetup -getinfo "Airport"

Manual Configuration
IP address: X.X.X.X
Subnet mask: 255.255.252.0
Router: X.X.X.X
IPv6: Automatic
IPv6 Link Local Address: fe80::XXXx:XXXX:XXXX:XXX
Ethernet Address: 00:30:XX:XX:XX:XX

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• Setting up and interface

- Enter

sudo networksetup -setmanual "Built-in Ethernet" 192.168.100.100 255.255.255.0 192.168.100.1

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• Tar

tar -cvzf images.tar "File Name"

-- unpack --

tar -xzf ~/filename.tar/

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• DHCP Netinfo - Network info

ipconfig getpacket en1

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• Logging elimination of specified text

tail -f /var/log/router.log| sed -e '/routername/d' -e '/other_router/d'
/d is a sed option to delete the whole line if it matches what's inside the two /'s

tail -f /logs/cisco-routers | egrep -v list

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• Grep through directory in search of specific text

grep -e 'aaa' -f *confg

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• sftp

sftp://username@host.domain.com:22/

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• Alias Address Ethernet Interface

sudo ifconfig en0 inet X.X.X.X netmask 255.255.252.0 alias

** Remove
sudo ifconfig en0 X.X.X.X netmask 0xfffffc00 broadcast X.X.X.X -alias

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• DNS Digging

495 dig axfr domain.com @disthost.domin.com | grep hostname
496 dig axfr domain.com @disthost.domin.com | sed -e '/^hostname/p'
497 dig axfr domain.com @disthost.domin.com | grep ^hostname
498 dig axfr domain.com @disthost.domin.com | grep ^hostname | sed -e '/MX/d'

**
dig axfr domain.com @disthost.domin.com | grep ^hostname | sed -e '/MX/d'

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• Piping output to file

sudo tcpdump -i en1 > ~/Desktop/output

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• Grep -

grep "Nov 22" /var/log/system.log | grep -v "words to omit"|grep -v "more words|grep -v "even more words"
-or -
tail -f /var/log/router.log | egrep -v "line 103|line 104"

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• Netinfo

Determining what Netinfo Server a client has bound to:
sudo lsof -i | grep lookupd

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Man pages stored in /usr/share/man/man8/


____+_________+_______

Revision control:
/usr/local/tftp/configs - Location of the files
rcsdiff rotuername.domain.com-confg - gets you the revision number
rcsdiff -r1.2 router.domain.com-confg - once you have that revision number you can compare the changes
co -p1.11 router.domain.com-confg - Complete revision of a config

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• SSH to Router with Secure ID Auth

ssh -l user X.X.X.X

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• Searching with Grep

grep gnutella *.acl

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• Clearing the contents of a file

cat /dev/null >/var/log/filename.log

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• Active Connections on a box:

netstat -a -f inet -p TCP | grep -i established

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• Port Check

nc -z -v hostname.domain.com 443

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• Tar Files

tar -cvvf home.tar home/

In the above example command the system would create a tar file named home.tar
in the directory you currently are in of the home directory.

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• Extracting the files from a tar file:

tar -xvvf myfile.tar

In the above example command the system would uncompress (untar) the myfile.tar file in the current directory.

ssh preshared key generation -

http://developer.apple.com/documentation/developertools/Conceptual/XcodeUserGuide/Contents/Resources/en.lproj/13_SSHEnvironment/chapter_953_section_1.html

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• Making a cool .bash_profile:
alias servername="ssh yourname@servername.com"
alias ls="ls -lGitur"
alias q="exit"
alias tftp="cd /private/tftpboot"
alias open="cd /Applications"
alias tunnel="ssh username@servername.com -D 2222"

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• Listing open connections you haveon your system:

lsof -i

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• Updating your path (bash) with:

% echo 'PATH=$PATH:/usr/local/bin' >> ~/.bash_profile
% source .bash_profile

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• MD5 Hash

openssl passwd -1 -table -salt "73u3" "cisco"

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• Show system Version (Mac OS X)

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