xssfox

If you follow my partners YouTube channel, Drop Table Adventures, you’ll be well aware that they have been entering the “Around the Bay” cycling event for several years now. Specifically “The Classic” route. This is a 220km circuit….. around the (Melbourne) bay.

This year on a bit of a whim, and within 5 days until the event I decided to buy a ticket for the 100km route. Then I checked the weather. I should have checked the weather first.

The 100km route leaves Albert Park, over the West Gate bridge to Williamstown, back across West Gate, follows the bay towards Mordialloc before returning to Albert Park.

A 100km ride is big for me. The last time I rode 100km was in high school. Made even more challenging in that I hadn’t trained for this. But I felt strong when I purchased the ticket.

Challenges:

• Scoliosis - riding long distances has historically been extremely hard on my back
• No training - I did a 40km social and slow ride about a month prior, and a 20km about 2 weeks prior
• Still somewhat recovering from my last bike crash
• I don’t really have much experience in group riding
• 3 days prior I managed to give myself food poisoning (stomach related fun seems to be a reoccurring problem when I enter events it seems)
• The 100km route requires crossing the West Gate twice - so a bit of elevation change compared to just riding the bay trail

On my side:

• Have been keeping fairly fit, swimming, short runs
• Competing in the commuter cup 2-3 days a week

Prep

To give myself the best shot of making the distance I stripped my bike of the lock, front and rear racks. Given the weather I left the mud guards on (more of a courtesy to other riders but seems I was alone here). With no racks, I had a small saddle bag which carried a toolkit, bacon strips, tyre levers, a tube, my phone and a pump.

For hydration and fuel I carried… an AARNet water bottle. I decided to rely on the rest stops for fuelling needs. In hindsight I probably should have packed at least a single gel.

Go

Since I had traveled with Droppy and Alex to the event, I was very early for the 100km start. This meant I found myself at the start of the pack. It’s not a race so it doesn’t matter so much, but it certainly grouped me with some riders that were probably a little bit fitter than me.

Leaving the start line I was filled with “oh god what have I gotten myself into” as I kept up with some very expensive bicycles being ridden by people that at the very least looked the part. I on the other hand was wearing a loose fitting running top and running tights with my budget gravel bike. There was some slight drizzle but it was otherwise not bad conditions to ride in. Moving speed was around 30km/hr.

Hitting the west gate though and that speed dropped right back to 16-20km/hr, but I was still keeping up with the main pack. The pack was cruising at closer to 28km/hr after the bridge which was a bit closer to what I could handle.

At 18km we hit the first rest stop - I decided to keep riding through. The pack thinned at this point but I clearly wasn’t the only one continuing through. Back over the bridge and on the other side I felt that my legs were a bit more like Jell-O™ now (40km in). Unfortunately the pack split up a bit due to traffic lights and eventually I was practically alone. At this point I was considering skipping the next stop and continue straight onto Mordialloc (70km in).

However at 45km logic prevailed and I realised I needed fuel and a top up of my water. So when the 50km Elwood rest stop came up I entered. At this point I found myself in an interesting situation - I was too fast to be in the casual riding groups and too slow to keep up with the serious groups. At Elwood rest stop I entered while they were practically still setting up. I think I saw two other cyclists. I was still able to grab a banana and some water. Was hoping that there would be some hydralite. Onwards!

This next section between Elwood and Mordialloc was horrible, the worst even. I’m not sure if it was just because I was low on energy or the way the elevation changes occur, but speed dropped significantly on the slight uphills. The downhills didn’t feel like they lasted for long. A couple of packs over took me here, I tried to keep up for a bit but just couldn’t. Regardless still averaging around ~25km/hr. I was riding alone for pretty much all of this section.

Arriving at Mordialloc (70km) I was sore. I knew I had to spend some time at this stop. I grabbed some crisps, trail mix, and a gel. While eating I spent some time sitting and standing to give the muscles that keep my back in check a break. Legs were feeling ok, but not strong. During this time I overheard that rain would be coming at 11am. At this point I decided that maybe, just maybe I could make it back dry.

While the Elwood/Mordialloc stretch was the hardest, the Mordialloc to finish stretch was the sorest. At 80km my back just said no. I considered stopping for a break. I felt I was close enough that I could just suffer a bit more.

I noticed on my bike computer that my average speed was around 25.3km/hr. This shocked me a little as I went into this thinking that my speed would be closer to 20km/hr. My immediate thought was “maybe I can get 100km in under 4 hrs”. Could I keep up my pace?

No. By 90km it had lowered to 25.0km/hr. All was not lost though, the elevation flattens out and I was able to keep my speed up. Just one tiny problem. The much more casual 50km riders were now mixed in, combined with more traffic lights. The average speed kept slipping lower and lower, the rain started, and my focus became just making it back. I’m glad I made this decision - the traffic was just too busy and the interruptions too great to make it.

Coming in to Albert Park for the finishing lap, it was wet. I was cold from waiting for traffic lights. My Garmin read 99.3km. This was going to be unsatisfying. So instead of ending the ride, I quickly funneled through the finish then rode to our car. Making up the missing 700m + giving me shelter from the rain.

The pain

Surprisingly my back recovered fairly quickly. Just being off the bike was enough. My right leg however was not. Any slight twist on it when load bearing was extremely painful. I was extremely concerned that I had undone a bunch of recovery.

The next day was a relief. While there was some amount “somethings not right here” feelings, the issue had mostly gone away. Hopefully this trend continues. I generally feel like my body should feel a lot worse than it is today.

The bike

So how did the bike hold up? It was a dream with one tiny hiccup. Shifting became unreliable about 50km in. I think this is just a cable tension issue and is easily fixed, but I didn’t want to risk making it worse during the day. I figured I could just double shift then back one when it didn’t change. Could be as simple as the wheel sitting slightly differently after being reassembled post transported.

Again?

I won’t say no, but it’s unlikely. This really pushed the limits of my back, just a bit more than I feel comfortable with.

The event was extremely enjoyable. Maybe I’ll sign up for the 50km instead.

The stats

One more thing

Remember that desire to get under 4 hours? Well, since I get to set the rules… if you look at Garmin’s recorded moving time (aka, removing all the traffic light stops) we get:

I haven’t been in this sort of industry for awhile now, so I might be a bit of out of touch but I imagine this hasn’t changed since I left.

I saw a fedi post recently that talked about how corporate wouldn’t let them purchase a little switch for their office to make file transfers quicker. I won’t link it here because what I’m going to dive into isn’t the point of that post but I do have experience with why corporate don’t want you to plug in that 5 port Netgear switch that everyone buys¹.

BTW, IT is likely doing their best and balancing reliability, cost and supportability, along with a dozen other user issues. Regardless your company should help you solve the problems you have with infrastructure rather than just saying no.

Today we’ll be focusing specifically on the layer 2 (ethernet) technical details. We won’t be talking about the security, privacy, safety, or physical reasons. There’s a lot of legacy reasons leading to cause of this, so before we dive in we need to understand some context as to why a corporate network have separate network segments and how this impacts the fault conditions we’ll discuss.

If you work in a big building like mine, or a large campus you could hundreds to thousands devices connected to the network. Devices broadcast a lot of traffic. This traffic goes to all devices. This includes working out what IP address should assigned, what hardware address maps to what IP address, and things performing network discovery so that icons pop up to indicate there’s a printer or streaming device available. This traffic is all sent to every device on the same segment. Scaling this up to thousands of devices would cause a lot of wasted bandwidth.

Even if we have enough bandwidth to handle all the screaming from devices, we still want to make sure our system is reliable. If some of the incidents I’m going to describe below happen, we want it to impact a smaller set of users, rather than the whole network.

Ok. Lets start building our network. One switch can’t handle all our users, so lets go down to our local office supply store and pick up the cheapest network switch we can find.

Perfect. Then someone accidentally kicks the switch with their foot, stuff gets unplugged and there’s a rush to plug everything back in. We then end up with this.

The two switches end up plugged into each other. If you bought switches with spanning tree protocol (STP), then this is fine and will work². If you didn’t, we end up with a loop.

What happens is the ethernet frames get sent back and forwards forever building up until there’s no bandwidth left for any legitimate data. This is why we have spanning tree protocol.

Problem solved! Just buy switches with spanning tree…. except… it’s a little more difficult.

Consider this example. We add our switch into this complex network.

We plug in our pirate network switch. And suddenly the whole network stops for a minute or two. What just happened is that spanning tree had to reconfigure itself. This is because your switch happened to be configured with a lower priority than others and became the root switch.

You’ll notice that not only did we get hit with spanning tree reconfiguring, but also our pirate switch has forced the algorithm to select slower links than we would otherwise have available.

To make matters worse, there are multiple different types of spanning tree: STP, R(apid)STP, M(ulti)ST, P(er)V(lan)ST.

Lets go back to a dumb switch, that seems easier. What if we were to install it like above, but someone accidentally connects the dumb switch to two different switches on the network at the same time.

What happens here is that the spanning tree enabled switches can see a link to another spanning tree via the dumb switch. They aren’t aware of the dumb switch. This can cause issues like a large amount of traffic going via your tiny switch.

Ok. Maybe we are careful and we don’t connect another switch to ours. Someone finds a loose cable and accidentally plugs the switch into itself.

Of course we have a loop. However since spanning tree thinks everything is ok, that traffic is also transmitted to the rest of the network. From the point of view of spanning tree, there isn’t a network switch there. Even if the wired network can handle the bandwidth, the WiFi access points might not be able to.

Another little quirk is that many switches are configured with a system called “port fast”. Usually spanning tree waits a period of time to figure out if there is a network switch on the other end. Port fast assumes the port is meant for a device and skips that learning/listening phase. This means that loops can exist for some time before a loop is detected. Port fast exists so that computers don’t have to wait forever to get a DHCP lease to get going.

To summarise all of this

• All switches need to be spanning tree enabled for spanning tree to be effective
• All switches need to be configured correctly so that the suitable paths are selected
• For a stable network, switches need to be configured to prevent pirate switches

Preventing pirate switches

A number of configuration options exist to to prevent issues when switches are connected:

• BPDU Guard : BPDUs are the messages sent by spanning tree. If a switch detects this on a port that has been designated as a user port it will disable the network port and requires manual reset.
• Root guard : This flags which ports on the switch we expect to find the spanning tree root. We disable ports that would have resulted in a root we didn’t expect
• Loop guard : Detects packet loops and disables the port
• Setting low spanning tree priorities
• Mac address limit : We can detect dumb switches by counting how many devices a switch port can see

Bonus 0: VLANs

How your network is configured to handle spanning tree and VLANs could be one of many many many configurations. The network might have VLANs have cover only some switches for some VLANs. Spanning tree could be running per VLAN, or a group of VLANs. This means connecting a spanning tree switch might only impact one spanning tree instance leaving loops possible in other VLANs.

Bonus 1: Unidirectional Link Detection

Unidirectional what? We like to think of network links as working or not. But there’s a secret third option - working only in a single direction. This is especially common with fibre optics and media converters.

From spanning trees point of view, it can’t see a switch on the other side and will start forwarding packets towards it, thus causing a loop. We use UDLD (Unidirectional Link Detection) to prevent this.

Bonus 2: Virtual machines

Virtual machine systems, especially complex ones, can introduce their own switching and bridging to the equation which can cause loops when trying to configure redundant links or port aggregation. They also pose other possible threats such as duplicate virtual mac addresses. Typically these will trigger the mac address limits on ports.

Bonus 999999: what about TRILL? SPB?

Network vendors don’t have your best interests in mind and decided to fuck the standards for their own vendor lock in needs.

Bonus 1000000: UniFi have a web interface to make configuring this stuff simple

So did Cisco in like the 90s. Much like UniFi it also sucked at enterprise scale.

Other reasons

So while we discussed just one technical aspect as to why just yeeting random switches into a network is a bad idea, there’s many more.

• On going maintenance - firmware updates/patching
• Security - if its a managed switch (common for STP support) then ensuring its configured securely
• Privacy - we don’t want to open the network up to sniffing of traffic
• Safety - Testing and tagging, cable tripping hazards
• More technical - Sometimes what people think are switches are routers and provide a rouge DHCP server

tl;dr: it’s probably stolen

Facebook marketplace seems like the perfect place to grab a bargain on preloved bicycles looking for a new home. But is that new bicycle stolen property? Facebook’s lack of regulation, enforcement and inherent design makes it the perfect platform for stolen goods. Combine that with police unwillingness to aid in bike theft recovery (when compared to automobiles), it’s very common to see stolen bicycles on Facebook Marketplace.

Before we go to far, the below checks aren’t perfect. They are signals to be cautious but not definitive proof that a good was stolen or not.

Additionally the person selling the item might not even be aware it was stolen. They might have purchased it from someone else, it might have acquired from a police auction, it could be from an estate sale, or some other legitimate means.

Finally, we also need to consider why bikes get stolen. With the increased cost of living, housing crisis and lack of social support - people are going to resort to any means to get by. This isn’t excusing their actions, but provides context as to why we might be in this position start with.

PropertyVault

First up - the obvious. Has the bicycle been listed on a stolen bicycle websites. In Australia the goto is PropertyVault. If you do find out that the bicycle you’re interested in is listed on PropertyVault then please fill out the contact form on the site. Take screenshots of the Facebook listing in case it is removed.

Dodgy spray paint

For low end bikes, it’s not uncommon for bicycles to be spray painted to remove all discernible markings and customisation. The thought process I think here is that they can sell it has a generic bicycle without being caught or detected from selling “your” bike. I’m really not sure who buys these - but highly likely to be stolen. Often you see overspray on cranks, chain, spokes because disassembly isn’t trivial and who has time for that.

Selling a lot of bikes

The average person doesn’t have a stockpile of 20 bikes they are trying to sell. There’s certainly people who do like bikes, like repairing and enjoy selling them to get people riding so you do need to use some judgement here. Some ways of determining legitimacy further: are they operating under a company? Do they seem to have a workshop? Do the descriptions seem like they are written by someone who knows/likes bikes?

It’s also worth looking at sold history. Even though a seller might only have 3 bikes up for sale, they might have sold many many more under the same profile.

Broken spokes / damage from lock

This is more common on bikes with Axa locks, but check for spokes being damaged. It’s very easy for spokes to be damaged when snapping locks through twisting or in the case of Axa, not realising its locked and trying to ride. There might also be evidence of where an Axa lock used to be mounted.

Missing e-bike charger

There are many e-bike charger standards and pretty much all e-bikes come with a charger. If the bike is being sold without the charger, or without the key to remove the battery, then good chance its been stolen off the street. The common story is “lost in house move” - which to be fair, is very likely. But treat with a lot of suspicion.

Selling lots of high value items

Is the seller also selling other suspicious items. Lots of powertools? Many iPads and iPhones? Gold and jewellery?

Profile doesn’t match actual person / sus

Facebook profiles that don’t match the sellers location or the person you meet doesn’t look like the profile picture. Maybe it’s a brand new profile, or no other items listed.

Poor / odd photos

High end bikes being sold with 2 crappy at night photos? Photo taken from within a public toilet? (I’m not even joking)

Incorrect model or part descriptions

Not looking for typos here but rather completely getting the model or parts wrong. In the below example this Aldi “ROAD 700” is being sold as a “RORO” because thats what it looks like when you look at the decal from the side. Another common example is when parts have been replaced. Sellers sometimes use the specifications found on manufactures websites rather than the actual parts installed. Some listings even have have bikes model or brand listed as one of the drivetrain parts like “Shimano”.

Same bike listed by multiple sellers

Some sus sellers use multiple accounts to sell their wares. Sometimes they get sloppy and sell the same product on multiple accounts.