831 Ethernet Broadband Router (CISCO831)

I just bought a Cisco 831 router. It was easy to reset and erase the password protected configuration using a DB9 to RJ45 console cable that was about $6 on eBay.

The early 831 models had 32mb of onboard DRAM by default with a single empty DIMM slot for 4mb, 8mb, or 16mb upgrades that add up to 48mb. Later 831 models came with 64mb of onboard DRAM with the same single slot for 4,8, and 16mb memory modules yielding a possible total of 80mb. The extra 16mb DRAM was very cheap.

Not so cheap was the so called Strata flash memory module. By default, the 831 comes with 8mb onboard flash memory and a 4mb flash memory module for 12mb total. Its possible to buy 8mb or 16mb replacement module for a total of up to 24mb of flash memory. The 16mb Strata flash cost me about $60 from an eBay seller offering a 3rd party replacement - cheap if you contrast it with other vendors.

Many auctions will not say which type of 831 they are offering and will not report which memory modules come with the unit. My router was advertised as 32mb but came with 64mb - a pleasant surprise. The flash was advertised as 8mb but was actually 12mb (it had a 4mb flash card). So take what you read with a grain of salt.

I cannot yet report how well the router works under load but we'll see. The dated 831 was worth the risk given its low price used. In the end, with the extra DRAM and Flash memory, I could have justified purchasing an 871 instead for about $50 more depending on the auction. Happy hunting.

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okay, here is a one week update
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I got the 831 router, 16mb dram, 16mb flash, and console cable (total 80mb dram, 24mb flash). I scrounged around for a new IOS 12.4(11)T which is about 11mb in size - this is why I needed more than the default 12mb flash memory.

I configured the router to use a cable modem, NAT, NAT rule for incoming torrent connections (single port with uTorrent), DHCP Service, and NTP time sync with external time servers. I then stress tested (in a slow and deliberate fashion) the router by increasing the number of torrents and the number of torrent connections - no problem. Router was rock steady.

However, I had problems with web pages taking up to two minutes to load. It was because I had put a default route that would direct traffic out the WAN interface. However, the WAN interface already had a default route assigned via DHCP from my ISP (charter). Removing the static route was the cure - that took two days to figure out. Now, its working like a charm.

In the long run the Cisco 831 is limited by its 10 mbs WAN interface. I'm at 5 mbs and in a few years should be at 10 or above. However, buying the Cisco 831 at reduced prices helped me to understand what I should buy next. In the mean time, I have a great router at a great price (or so it seems after 1 week). Take care.