Chronological archive of briefs published in 2013.
It's enough to configure the extended ACL, and hit a question mark when you want to define a PORT, just to realize that there is an entire world of ACL configuration options that we never knew about.
Practical notes on ccie blueprint v5 announced — Cisco, Networking configuration, design, and troubleshooting guidance.
Probably most typical usage of IP SLA is to measure the and UDP Jitter and Echo, to make sure that the path is good enough to send the sensitive VoIP traffic.
Practical notes on pbr - policy based routing — Networking, Cisco configuration, design, and troubleshooting guidance.
Practical notes on ipv6 tunnels — Networking, Cisco configuration, design, and troubleshooting guidance.
From Cisco Docs: "Route dampening is a BGP feature designed to minimize the propagation of flapping routes across an internetwork.
Another way to make the BGP configuration easier by avoiding configuring the same command set on every router.
Step 1: Start with the Link-Local "Signature", which is FE80:: - For Link Local IPv6 Addresses
Loopback: ::1/128 Multicast: FF00::/8 Link Local: FE80::/10 - used for stateless auto-configuration, Neighbor discovery, Router discovery FC00::/7 Unique Local, Unicast (equivalent to the IPv4 private addresses), not...
Before the command has been applied the external (LSA5) subnet within the area 0 is seen as: sh ip ospf database external 6.0.0.0 OSPF Router with ID (1.1.1.1) (Process ID 1) Type-5 AS External Link States LS age:...
First there is an "old school" method of setting time on your IOS Device, which is fine if you're one of those :) clock set 16:50:00 15 NOVEMBER 2013 \Nov 15 16:50:00.000: %SYS-6-CLOCKUPDATE: System clock has been...
IRDP enables Routers to automatically discover the IP of their potential Default Gateway. It uses ICMP and Solicitation Messages.
GLBP is different from HSRP and GLBP, as in - it's more complex and gives more possibilities, such as LoadBalancing It's got 1 VIRTUAL IP, and VARIOUS MACs
Redundancy Protocol, Cisco Proprietary. Configuration is quite straight-forward, but there are many ways to tune it, in accordance with your needs: interface FastEthernet0/0 ip address 172.25.25.2 255.255.255.0...
VRRP Authentication is configured PER GROUP using the command "vrrp X authentication text PASSWORD", and the debug on the VRRP Pair router is as follows (before the authentication is configured on BOTH):...
Using the DHCP Pool configured on a IOS device is somewhat obsolete, but in cases of smaller companies where this solution is inevitable (or in a case such as mine, preparations for a CCIE exam) - you should know how...
Scalability for Stateful NAT feature allows Stateful Network Address Translation (SNAT) to control the Hot Standby Router Protocol (HSRP) state change until the NAT information is completely exchanged.
This approach is used when you want to configure NAT and integrate it with HSRP (enable the same NAT on all the routers that form the HSRP group).
Make sure you understand how this command works, because it´s quite a complicated principle because it works a bit "upside down".
This is a configuration that I´ve never implemented in any production environment, but I see quite a few cases where it can be usefull.
Port Address Translation (PAT) means using PORTS in order to NAT various Inside Local IPs to 1 Inside Global IP.
Do not forget to configure the "ip nat inside | outside" on the appropriate interfaces!
Inside Local - Private IP of the host in your Network Inside Global - Public IP that outside network sees your hosts as Outside Local - How the local network sees IP of the remote host Outside Global - Public IP of...
For all the Network Engineers out there who, like myself, scream inside whenever someone confidently declares that SDN is the future - Don´t panic...
Cisco Documents: SecurityAAASecure Shell Configuration Guide http://www.cisco.com/en/US/docs/ios-xml/ios/sec\usr\ssh/configuration/12-4t/sec-cfg-secure-shell.html
Cisco Docs: Securing User Services ConfigurationAuthentication Authorization and Accounting http://www.cisco.com/en/US/docs/ios-xml/ios/sec\usr\aaa/configuration/12-4t/sec-cfg-authentifcn.html
root primary - sets the priority to: if ROOT 24576 - sets to 24576 (priority 24576 sys-id-ext 12) if ROOT =< 24576 - sets to 4096 root secondary - sets the priority to 28762
Practical notes on multiple spanning tree protocol (mst) — Networking, Cisco configuration, design, and troubleshooting guidance.
Practical notes on private vlans — Networking, Cisco configuration, design, and troubleshooting guidance.
VLAN Membership Policy Server - provides a centralized server for selecting the VLAN for a port dynamically based on the MAC address of the device connected to the port.
Cisco Docs: Cisco Docs: Secure DATA PLANESecurity Configuration Guide: Unicast Reverse Path Forwarding http://www.cisco.com/en/US/docs/ios-xml/ios/sec\data\urpf/configuration/12-4t/sec-data-urpf-12-4t-book.html
Cisco Docs: Secure DATA PLANESecurity Configuration Guide:Zone-Based Policy Firewall http://www.cisco.com/en/US/docs/ios-xml/ios/sec\data\zbf/configuration/12-4t/sec-data-zbf-12-4t-book.html
BGP is all about tuning. The non-tuned BGP is basically a RIP, but once you adjust it to your needs - no other routing protocol can come even close.
\- PREFIX LIST: You define the PREFIX list, and apply the same prefix list to the BGP neighbor
^ \- START of Line $ \- END of Line | \- Logical OR \ \- ANY DELIMETER ? \- ZERO instances of the PRECEDING character \ \- ZERO OR MODE instances of the PRECEDING character + \- ONE OR MORE instances of the PRECEDING...
Community attribute is one of those non-standard BGP attributes that you really need to know well if you wish to use it.
This is a pretty complex BGP issue because you really need to know the BGP philosophy and maybe even have some basic experience in programming.
It's configured on PER-NEIGHBOR, or as described in the Previous Post - on the PER-PEER-GROUP basis.
When you need to prefer LESS the eBGP route - you need a way to tune it, because not many routing protocols "beat" the eBGPs Administrative Distance (20).
Two first things that are considered the "BGP configuration best practice" are to disable the SYNCHRONIZATION and disable the Auto Summarization.
It's a simple concept, just a group of neighbors we want to configure with the same group of parameters.
First of all, why was the concept of Route Reflectors introduced? It´s quite simple actually.
On the Multipoint Frame-Relay network the default OSPF type is NON-BROADCAST. This means that the OSPF Neighbors will not be formed like on the standard Broadcast Network Segment.
The big CON is that even though the Route is not added to the Routing Table - it will stay in the database, and it will be further propagated to the other OSPF Neighbors.
First lets make sure we're comfortable with the LSA types, because you will not understand Stubs before you understand LSAs 100%
GRE - Generic Routing Encapsulation, is a method of tunneling data from one router to another.
Practical notes on ofpf cost tuning — Networking, Cisco configuration, design, and troubleshooting guidance.
At this level I suppose you know how to configure the Virtual Link, and what is it's purpose.
Practical notes on ospf authentication — Networking, Cisco configuration, design, and troubleshooting guidance.
Like in OSPF - the configuration is done in the Interface Configuration mode. Unlike OSPF - EIGRP supports only MD5 authentication.
First a heads up - it's a bit complicated because there are just too many details... Subjective impression!
Variance is a EIGRP feature that enables UNEQUAL load balancing. The only condition that needs to be met is: Paths need to be in the routing table and MEAT THE FEASIBILITY CONDITION!
The EIGRP route summarization is done exactly the same like RIP summarization, which makes sense because both protocols have the Distance Vector nature.
The EIGRP timers are configured (a bit non-intuitive commands from my point of view) on the interface towards the EIGRP neighbor:
RIP offset list \- used to INCREASE the Hop Count. To implement: \- define the ACL defining the relevant routes \- set the Hop Count to be increased (by 13 in this case):
RIP (IPv4 versions) is a bit obsolete, I know, and very few production environments will use it as a "routing protocol of choice", but it´s also quite simple and there is simply no excuse for a Network Engineer to...
This was originally posted by another blog, router-switch.com and I must say that agree only partially.
Practical notes on top interview questions for network engineers, part 2 — Networking, Cisco configuration, design, and troubleshooting guidance.
From what I've read the 50% of passing the CCIE is knowledge and speed, and the other 50% is knowing how to organize yourself.
I remember when I was first getting into Frame Relay I had much trouble getting the concept of DLCIs, LMIs and how it all works, because it´s so much different then other L2-L3 protocols.
It's true, I've read millions of how-to stories. Ok, maybe not millions, cause there are currently like 17k R&S CCIEs in the world, but...
Practical notes on narbik in web-iou — Cisco, Networking configuration, design, and troubleshooting guidance.
Cisco Docs: Secure DATA PLANESecurity Configuration Guide:Cisco IOS Intrusion Prevention System http://www.cisco.com/en/US/docs/ios-xml/ios/sec\data\ios\ips/configuration/12-4t/sec-data-ios-ips-12-4t-book.html
Practical notes on ospf: area range v.s. summary address — Networking, Cisco configuration, design, and troubleshooting guidance.
When we are talking about the QoS Congestion Management and Avoidance, the three most important terms are: queuing, dropping and scheduling.
Practical notes on cisco waas part ii: configuration — Cisco, Networking configuration, design, and troubleshooting guidance.
Practical notes on cisco waas part i: wan link optimization: how does waas work? — Cisco, Networking configuration, design, and troubleshooting guidance.
Quality of Service (QoS) is the ability to provide different levels of performance for individual applications and services that run over the networks.
The routes can be advertised using the "network" command, but there is also another way. You can do an entire configuration on the Interface Level!