Layer 3
Latest News
12-12-2022: Is secured routing a market failure? [Geoff Huston]
Latest Articles
Anycast resource page. [ipSpace]
Link state routing protocol basics. [ipSpace]
IRB models: edge routing. [ipSpace]
Relationships between Layer-2 (VLAN) and Layer-3 (subnet) segments. [ipSpace]
Routing protocol implementation evaluation. [ipSpace]
Is it time to replace TCP in data centres? [ipSpace]
What causes ICMP redirects? [ipSpace]
Integrated Routing and Bridging (IRB) design model. [ipSpace]
Routing will never be a solved problem. [ipSpace] [Internet Dynamics]
Comparing TCP and QUIC. [Geoff Huston]
Older News
09-10-2018: Routing in dense topologies – what's all the fuss? [NANOG 74 YouTube]
05-06-2018: It's time to replace TCP. [Russ White] [APNIC Blog]
28-05-2018: EIGRP: a multi-vendor demo. [Network Computing]
22-05-2018: Facebook unveils network load balancer and provisioning tool. [Network Computing] [DC Knowledge]
17-01-2018: Google's 'QUIC' TCP alternative slow to excite anyone outside Google. [The Register]
27-05-2018: How much of the Internet is QUIC? [Russ White] [APNIC Blog]
15-11-2017: Facebook open sources its routing platform. [Network Computing]
10-10-2017: Routing protocols - a perfect example of RFC 1925 Rule 5. [ipSpace]
04-10-2017: New standards will shore up Internet router security. [Network Computing]
18-10-2016: Routing protocol migrations in a live data center. [NANOG 68 YouTube]
12-10-2016: Why I care about Segment Routing. [Russ White] [The Forwarding Plane]
11-05-2016: Introducing Open/R - a new modular routing platform. [Facebook]
13-01-2017: Response: Introducing Open/R. [EtherealMind]
08-09-2015: TCP is a wire-centric protocol being forced to cut the cord, painfully. [The Register]
25-08-2015: System routes Internet traffic around countries you don't trust. [HardOCP] [IEEE Spectrum]
24-06-2015: More leaky routes. [Geoff Huston]
30-01-2015: Addressing 2014. [Geoff Huston]
16-07-2014: New photonic router works by flipping reflective atom's lid. [The Register]
14-06-2013: Will SPDY solve web application performance issues? [ipSpace]
04-02-2013: Thoughts on Open EIGRP. [Packet Pushers]
31-01-2013: Why is Cisco bothering with “Open” EIGRP? [Packet Pushers]
22-01-2013: TCP MSS clamping -- what is it and why do we need it? [ipSpace]
28-05-2012: Virgin Media wipes out websites with routing blackhole. [The Register]
29-05-2012: Virgin Media flushes pipes clogged by piles of Spotify fans. [The Register]
19-02-2012: EIGRP -- auto summary. [EtherealMind]
27-01-2012: Prefix-independent convergence (PIC): fixing the FIB bottleneck. [ipSpace]
24-01-2012: Google takes on Internet standards with TCP proposals, SPDY standardisation. [Ars Technica] [Engadget] [ReadWriteWeb]
19-04-2012: What web users need to know about SPDY. [ReadWriteWeb]
20-04-2012: Using SPDY on your web server. [ReadWriteWeb]
15-07-2012: Facebook endorses Google's SPDY networking protocol. [cNet] [Wired]
07-08-2012: HTTP standards group looks to SPDY protocol to influence HTTP/2.0. [Engadget] [Mnot]
03-12-2012: IETF wants Google's SPDY protocol for HTTP 2.0. [The Register]
27-12-2011: TCP/IP over Lego model train. [ExtremeTech] [Engadget] [Hackaday]
27-11-2011: Routing protocols and computation in silicon. [EtherealMind]
23-04-2011: IP address can now pin down your location to within half a mile. [Ars Technica]
12-02-2011: The cyberweapon that could take down the Internet. [Gizmodo]
03-01-2011: The basics of EIGRP. [CCIE Blog]
15-12-2010: Where would you need GRE? [IOS Hints]
04-10-2010: Multiple EIGRP ASs in a VRF. [IOS Hints]
02-09-2010: Understanding third-party next-hop. [CCIE Blog]
23-08-2010: Source-based RTBH. [PacketLife]
09-08-2010: EIGRP feasible successor routes. [PacketLife]
03-08-2010: EIGRP myths debunked. [IOS Hints]
29-06-2010: The next generation of routing architecture. [CCIE Journey]
20-05-2010: Sharing ideas - GLBP and HSRP. [Etherealmind]
07-05-2010: Fast static route convergence. [IOS Hints]
15-04-2010: How basic are RIP timers? [CCIE Blog]
17-03-2010: A simple IPv4 prefix summarisation procedure. [CCIE Blog]
19-02-2010: RFC 5772: A set of possible requirements for a future routing architecture. [IETF]
03-02-2010: Pollution in 1/8. [RIPE Labs]
01-02-2010: Understanding IP prefix lists. [PacketLife]
24-01-2010: Issues with allocating from 1.0.0.0/8. [BGPmon]
04-01-2010: Routing table profiling. [PacketLife]
25-03-2009: How Google routes around outages. [DC Knowledge]
Older Articles
QUIC is not a TCP replacement. [ipSpace] [Bruce Davie]
How routers became bridges. [ipSpace]
Are routing protocols automation? [EtherealMind]
Living with small forwarding tables. [ipSpace]
Source routing on the edge. [ipSpace] [iNOG YouTube]
Telephone system is a bad example of hierarchical addresses. [ipSpace]
Higher levels of address aggregation. [ipSpace] [Geoff Huston]
Combining BGP and IGP in an enterprise network. [ipSpace]
Segment routing vs LDP in hub-and-spoke networks. [ipSpace]
Flow-based packet forwarding. [ipSpace]
Misconceptions about route origin validation. [ipSpace]
Cache-based packet forwarding. [ipSpace]
Going multipath without Multipath TCP. [benjojo]
ICMP redirects considered harmful. [ipSpace]
Packet forwarding 101: header lookups. [ipSpace]
What's an "address"? [Geoff Huston]
Layer 3 carrier Ethernet. [ipSpace]
Explicit null in segment routing. [Routing Craft]
Multi-threaded routing daemons. [ipSpace]
IP class is now in session. [Networking Nerd]
Hardware differences between routers and switches. [ipSpace, Response, ipSpace]
Anycast in segment routing. [Routing Craft]
Route replication the easy way. [Lost in Transit]
Introduction to network addressing. [ipSpace]
Unexpected interactions between OSPF and BGP. [ipSpace]
Unnumbered Ethernet interfaces - DHCP edition. [ipSpace]
Routing protocols - use the best tool for the job. [ipSpace]
Unnumbered Ethernet interfaces. [ipSpace]
Single-metric unequal-cost multipathing is hard. [ipSpace]
Packet forwarding and routing over unnumbered interfaces. [ipSpace]
Back to basics: unnumbered IPv4 interfaces. [ipSpace]
The history of IP interface addresses. [ipSpace]
BGP-free MPLS core with segment routing. [ipSpace]
Back to basics: do we need interface addresses? [ipSpace]
Segment routing segment IDs and MPLS labels. [ipSpace]
Using MP-TCP to utilise unequal links. [ipSpace]
Does unequal-cost multipathing make sense? [ipSpace]
Link-state routing protocols are eventually consistent. [ipSpace]
How to troubleshoot routing protocol session flaps. [ipSpace] [RoutingCraft: part 1]
Wrong subnet mask causing unicast flooding. [ipSpace]
Segment routing -- the movie. [The Forwarding Plane]
EIGRP behaviour with IP Unnumbered. [Lost In Transit]
Introduction to segment routing. [Network Collective]
Segment routing is many different things. [Packet Pushers]
Visualising major routing incidents in 3D. [NANOG 78 YouTube]
Heavy networking 491: real-life segment routing and PCE. [The Forwarding Plane]
Segment routing. [ipCisco]
IP fragmentation in detail. [Packet Pushers]
History of multipath TCP. [Russ White]
History of networking: DUAL. [Russ White]
History of TCP/IP. [Russ White]
Explain a migration from EIGRP to eBGP+OSPF. [Packet Pushers]
Why use BGP as a Clos underlay instead of ISIS? [Packet Pushers]
Do packet drops matter for TCP performance? [ipSpace]
IP Time to Live (TTL) and hop limit basics. [Packet Pushers]
Why is MPLS segment routing better than LDP? [ipSpace]
Introduction to segment routing. [Network Collective]
Why not OSPF for the Internet core? [Russ White]
How could an EIGRP Stuck In Active event ever happen in real life? [EtherealMind]
Segment routing anyone? [ipSpace]
History of networking -- routing software. [Network Collective] [Russ White]
Dynamic routing protocol types. [ipCisco]
Valley-free (or non-zigzag) routing. [ipSpace]
Understanding FR routing. [Russ White] [Packet Pushers]
Understanding the EIGRP command, “metric rib-scale”. [INE]
Source address dependent routing. [Russ White] [APNIC Blog]
Routing loop - failure by design. [PacketU]
A closer look at the IP header. [Russ White] [APNIC Blog]
Avoid summarisation in leaf-and-spine fabrics. [ipSpace]
Is eBGP really better than OSPF in spine/leaf fabrics? [ipSpace]
Floating static route and default route configuration. [ipCisco]
Is OSPF or IS-IS good enough for my data centre? [ipSpace]
Why is feasibility condition less than? [Russ White]
IPv4 subnetting best practices. [Network Computing]
Deconfusing the static route. [Russ White]
Routing design: OSPF or EIGRP? [NetCraftsmen]
Disjoint path routing and LP. [Packet Pushers]
Is NAT a bad thing? [NetCraftsmen]
History of networking: fast reroute. [Network Collective]
TCP vs UDP. [ipCisco]
Inter-VLAN routing with router on a stick. [ipCisco]
SVI - Switch Virtual Interfaces. [ipCisco]
OSI and TCP/IP models. [ipCisco]
TCP/IP model. [ipCisco]
TCP congestion signatures. [Russ White] [APNIC Blog]
The power of network disaggregation. [Network Computing]
Can routing be oversimplified? [Networking Nerd] [Russ White]
Segment routing. [Russ White] [Network Collective]
Route leaks. [Russ White] [CircleID]
An opinion on offense against NAT. [Networking Nerd]
WISP Design: Using eBGP and OSPF transit fabric for traffic engineering. [EtherealMind] [MikroTik YouTube]
A contrarian view on NAT. [jpSpace] [Geoff Huston]
History of networking - EIGRP. [Network Collective]
IP subnetting with examples. [ipCisco]
IPv4 addressing. [ipCisco]
IP and Layer 3 overview. [ipCisco]
Home network IP address allocation and Internet connection. [ipCisco]
To BFD or not to BFD? [ipSpace]
DHCP overview. [ipCisco]
Reducing the number of transported routes. [ipSpace]
RIPng configuration example on Cisco IOS. [ipCisco]
EIGRP for IPv6. [ipCisco]
Configuration example on Cisco IOS. [ipCisco]
Do remote LFAs really solve microloops? [Russ White]
The TCP tortoise. [Russ White] [LinkedIn Engineering]
Source destination routing. [Russ White]
Tools for TE with EIGRP. [Packet Mischief]
Cutting through the segment routing hype. [Russ White] [IETF Journal]
When is a connected route not used? [Packet Mischief]
Open Source routing at NANOG. [Russ White] [NANOG YouTube]
All you ever wanted to know about EIGRP. [Network Collective]
Hashing on broken assumptions. [NANOG YouTube]
Lost in fat tree forest and route out. [NANOG YouTube]
Segment routing. [NANOG YouTube]
Anycast and latency. [Russ White]
Choosing a routing protocol. [Network Collective] [YouTube]
Microloops explained. [Russ White] [Packet Pushers]
Interim forwarding loops in OSPF or IS-IS. [ipSpace]
Choosing a routing protocol. [Russ White] [Network Collective]
IP addresses, subnet masks, and default gateways. [Network Computing]
General network challenges -- and IP/TCP/UDP operations. [Packet Pushers]
Five subnetting benefits. [Network Computing]
Segmenting Layer 3 networks with VRFs: [PacketU]
Failover mechanism basic [Packet Pushers: part 1]
Could you use IS-IS instead of BGP for routing on hosts? [ipSpace]
Network performance analysis: TCP MSS. [Network Computing]
I2RS and remote triggered black holes. [Russ White]
Comparing dynamic routing protocols. [Network Computing]
Use VRFs to solve routing-on-hosts challenges. [ipSpace]
Routing with EIGRP: [ipCisco]
What is segment routing? [Russ White] [NetCraftsmen]
Why would I use BGP and not OSPF between servers and the network? [ipSpace]
Routing with IS-IS: [ipCisco]
Layer 2 routing -- haven't we been here before? [Russ White]
The difficulty of routing around Internet surveillance states. [Schneier] [arXiv]
Testing the EIGRP Feasibility Condition (FC). [PacketU]
Is there always a feasible successor in EIGRP? [EtherealMind]
TCP/IP is a lossy protocol. [EtherealMind]
On the lossiness of TCP. [ipSpace]
Reserved internal address ranges. [Network Sherpa]
DR vs DIS: what's the difference? [Russ White]
Should routing react to the data plane? [Russ White]
Enterprise IP routing best practices. [Network Guru] [NetworkOp]
Network redundancy protocols: [ipCisco]
BGP or OSPF -- does topology matter? [ipSpace]
Fragmentation. [Geoff Huston]
Redistribution of named and tagged static routes. [Network Sherpa]
Packet- and flow-based forwarding. [ipSpace]
DHCP details you didn't know. [ipSpace] [Fragmentation Needed]
Using BFD to track WAN status and change HSRP priority. [Lost In Transit]
Do we still need subnets in virtualised networks? [ipSpace]
Multipath TCP. [Geoff Huston]
ARP processing in L3-only networks. [ipSpace]
Traceroute and not-so-equal ECMP. [PacketLife]
Re-architecting L3-only networks. [ipSpace]
Five functional facts about EIGRP. [PacketMischief]
EIGRP "FD is Infinity". [PacketMischief]
Choosing a route: order of operations. [PacketMischief]
Lab: iBGP and OSPF traffic engineering. [PacketMischief]
Let's get rid of the thick yellow cable. [ipSpace] [Mark Burgess]
Discard routing for RFC1918 addresses. [PacketU]
The longest match rule. [PacketU]
Improving ECMP load balancing with flowlets. [ipSpace]
How many hosts in a VLAN or IP subnet? [EtherealMind]
Coping with byzantine routing failures. [ipSpace]
Default gateway, default route, and default network. [Ether Network Training]
EIGRP route filtering using route maps. [Ether Network Training]
EIGRP passive interfaces. [Ether Network Training]
Advice on inter-AS routing. [Reddit]
Cisco IOS – understanding IGP network statements. [PacketU]
Who understands network statements? [PacketU]
NFV: will vRouters ever replace hardware routers? [EtherealMind]
Load balancing on congestion, OSPF over MPLS. [StackExchange]
Configuring a Cisco ASA 5505 for routing. [StackExchange]
BGP, multipathing, and possibly OSPF. [StackExchange]
Why is RIP not scalable? [StackExchange]
CIDR /31 use question. [Reddit]
Does uRPF make sense in ISP networks? [ipSpace]
Unicast RPF on the edge. [StackExchange]
EIGRP is restricted to stub configurations only on this platform. [StackExchange]
Do today's routers prevent fake IP headers? [StackExchange]
Trying to test a virtual lab VRRP configuration for STP issues. [StackExchange]
Cisco - display ALL routes using a single command. [StackExchange]
Best practice for the combination of HSRP and ECMP. [StackExchange]
How to find the source of increased latency? [StackExchange]
Can one configure several static EIGRP Neighbors on one interface? [StackExchange]
RIP routing is broken between two routers. [StackExchange]
EIBGP load balancing. [ipSpace]
IPv4 address space planning best practices. [StackExchange]
Route servers and looking glasses -- what are they? [StackExchange]
Protocols: EIGRP vs OSPF. [StackExchange]
Teaching TCP/IP headers with Lego. [BoingBoing] [Righteous IT]
How would you like to configure policy-based routing (PBR)? [ipSpace]
The routing security battles intensify. [IGP]
EIGRP loop prevention logic. [ipSpace]
A slight problem with distributing EIGRP into MP-BGP. [PacketLife]
EIGRP vs OSPF - take 2. [EtherealMind] [Cisco Blog]
Simultaneous tunneled and native Internet access. [PacketLife]
Is a layer-3 switch more than a router? [ipSpace]
EIGRP: an MBA-like perspective. [ipSpace]
What's the best IP address to ping to test my Internet connection? [EtherealMind]
A data center that mimics a mansion. [DC Knowledge]
IP renumbering in disaster avoidance data center designs. [ipSpace]
Is your network WAN optimisation really helping? [DC Knowledge]
Cisco Performance Routing (PfR) / Optimised Edge Routing (OER). [CCIE Blog: part 1]
BGP next-hop processing. [IOS Hints]
Dynamic failover between two WAN links. [PacketLife]
BGP/IGP network design principles. [IOS Hints]
Policy-based vs Route-based VPNs. [PacketLife: part 1, part 2]
TCP slow start. [PacketLife]
NHRP convergence issues n multi-hub DMVPN networks. [IOS Hints]
DMVPN: how to get from zero to hero? [IOS Hints]
VPN network design. [IOS Hints: part 1, part 2]
DMVPN phase 2 fundamentals. [IOS Hints]
Configuring OSPF in phase 2 DMVPN network. [IOS Hints]
DMVPN phase 1 fundamentals. [IOS Hints]
OSPF configuration in phase 1 DMVPN network. [IOS Hints]
Sometimes you need to step back and change your design. [IOS Hints]
TCP flags: PSH and URG. [PacketLife]
Loop-free alternate routes. [EtherealMind]
How did we ever get into this switching mess? [IOS Hints]
How Internet peering works. [Comcast]
RIP cheat sheet. [PacketLife]
© Robert Larsen. All rights reserved.