Since the early 1990s, we’ve watched as the number of entries on the Internet routing table has steadily grown. It wasn’t that long ago (2008) that the table reached 256k routes, triggering action by network administrators to ensure the continued growth of the Internet. Now we have passed that another significant milestone — the global routing table has passed 512,000 routes.
As an industry, we’ve known for some time that the Internet routing table growth could cause some networking products to run out of resources, in particular the TCAM. TCAM is a very important component of certain network switches and routers that stores routing tables. It is much faster than ordinary RAM (random access memory) and allows for rapid table lookups.
Networking Product Implications
No matter who provides your networking equipment, it needs to be able to manage the ongoing growth of the Internet routing table. We recommend confirming and addressing any possible impacts for all devices in your network, not just those provided by Cisco. The products that could be affected include those with a default configuration supporting 512k routes. From Cisco’s perspective, this includes:
- Cisco Catalyst 6500 Switches
- Cisco 7600 Series Routers
- Cisco ASR 9000 Series Aggregation Services Routers configured with Trident-based line cards (typhoon-based line cards are not affected)
- Cisco ASR 1000 Series Aggregation Services Routers with 4GB (devices with 8GB or RAM or higher can scale to up to 1,000,000 routes)
The Good News – Workarounds Are Available!
Cisco has published information on several workarounds that can be applied by our customers, including changing the default configuration for affected devices. In some cases this may require a reload of the device or line card. See the full Cisco support article at: The size of the Internet global routing table and its potential side effects